rustc_codegen_ssa: Better code generation for niche discriminants.
In some cases we can avoid arithmetic before checking whether a niche represents an untagged variant. This is relevant to #101872
This commit is contained in:
Michael Benfield
parent
5b82ea74b7
commit
51918dcc51
3 changed files with 373 additions and 51 deletions
112
src/test/codegen/enum-match.rs
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112
src/test/codegen/enum-match.rs
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// compile-flags: -Copt-level=1
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// only-x86_64
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#![crate_type = "lib"]
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// Check each of the 3 cases for `codegen_get_discr`.
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// Case 0: One tagged variant.
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pub enum Enum0 {
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A(bool),
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B,
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}
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// CHECK: define i8 @match0{{.*}}
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// CHECK-NEXT: start:
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// CHECK-NEXT: %1 = icmp eq i8 %0, 2
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// CHECK-NEXT: %2 = and i8 %0, 1
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// CHECK-NEXT: %.0 = select i1 %1, i8 13, i8 %2
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#[no_mangle]
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pub fn match0(e: Enum0) -> u8 {
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use Enum0::*;
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match e {
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A(b) => b as u8,
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B => 13,
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}
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}
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// Case 1: Niche values are on a boundary for `range`.
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pub enum Enum1 {
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A(bool),
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B,
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C,
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}
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// CHECK: define i8 @match1{{.*}}
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// CHECK-NEXT: start:
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// CHECK-NEXT: %1 = icmp ugt i8 %0, 1
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// CHECK-NEXT: %2 = zext i8 %0 to i64
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// CHECK-NEXT: %3 = add nsw i64 %2, -1
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// CHECK-NEXT: %_2 = select i1 %1, i64 %3, i64 0
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// CHECK-NEXT: switch i64 %_2, label {{.*}} [
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#[no_mangle]
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pub fn match1(e: Enum1) -> u8 {
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use Enum1::*;
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match e {
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A(b) => b as u8,
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B => 13,
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C => 100,
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}
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}
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// Case 2: Special cases don't apply.
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pub enum X {
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_2=2, _3, _4, _5, _6, _7, _8, _9, _10, _11,
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_12, _13, _14, _15, _16, _17, _18, _19, _20,
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_21, _22, _23, _24, _25, _26, _27, _28, _29,
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_30, _31, _32, _33, _34, _35, _36, _37, _38,
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_39, _40, _41, _42, _43, _44, _45, _46, _47,
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_48, _49, _50, _51, _52, _53, _54, _55, _56,
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_57, _58, _59, _60, _61, _62, _63, _64, _65,
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_66, _67, _68, _69, _70, _71, _72, _73, _74,
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_75, _76, _77, _78, _79, _80, _81, _82, _83,
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_84, _85, _86, _87, _88, _89, _90, _91, _92,
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_93, _94, _95, _96, _97, _98, _99, _100, _101,
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_102, _103, _104, _105, _106, _107, _108, _109,
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_110, _111, _112, _113, _114, _115, _116, _117,
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_118, _119, _120, _121, _122, _123, _124, _125,
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_126, _127, _128, _129, _130, _131, _132, _133,
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_134, _135, _136, _137, _138, _139, _140, _141,
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_142, _143, _144, _145, _146, _147, _148, _149,
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_150, _151, _152, _153, _154, _155, _156, _157,
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_158, _159, _160, _161, _162, _163, _164, _165,
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_166, _167, _168, _169, _170, _171, _172, _173,
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_174, _175, _176, _177, _178, _179, _180, _181,
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_182, _183, _184, _185, _186, _187, _188, _189,
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_190, _191, _192, _193, _194, _195, _196, _197,
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_198, _199, _200, _201, _202, _203, _204, _205,
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_206, _207, _208, _209, _210, _211, _212, _213,
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_214, _215, _216, _217, _218, _219, _220, _221,
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_222, _223, _224, _225, _226, _227, _228, _229,
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_230, _231, _232, _233, _234, _235, _236, _237,
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_238, _239, _240, _241, _242, _243, _244, _245,
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_246, _247, _248, _249, _250, _251, _252, _253,
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}
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pub enum Enum2 {
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A(X),
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B,
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C,
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D,
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E,
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}
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// CHECK: define i8 @match2{{.*}}
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// CHECK-NEXT: start:
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// CHECK-NEXT: %1 = add i8 %0, 2
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// CHECK-NEXT: %2 = zext i8 %1 to i64
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// CHECK-NEXT: %3 = icmp ult i8 %1, 4
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// CHECK-NEXT: %4 = add nuw nsw i64 %2, 1
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// CHECK-NEXT: %_2 = select i1 %3, i64 %4, i64 0
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// CHECK-NEXT: switch i64 %_2, label {{.*}} [
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#[no_mangle]
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pub fn match2(e: Enum2) -> u8 {
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use Enum2::*;
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match e {
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A(b) => b as u8,
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B => 13,
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C => 100,
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D => 200,
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E => 250,
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}
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}
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114
src/test/ui/enum-discriminant/get_discr.rs
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114
src/test/ui/enum-discriminant/get_discr.rs
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@ -0,0 +1,114 @@
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// run-pass
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// Now that there are several variations on the code generated in
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// `codegen_get_discr`, let's make sure the various cases yield the correct
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// result.
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// To get the discriminant of an E<X1> value, there are no shortcuts - we must
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// do the full algorithm.
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#[repr(u8)]
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pub enum X1 {
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_1 = 1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _16,
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_17, _18, _19, _20, _21, _22, _23, _24, _25, _26, _27, _28, _29, _30, _31, _32,
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_33, _34, _35, _36, _37, _38, _39, _40, _41, _42, _43, _44, _45, _46, _47, _48,
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_49, _50, _51, _52, _53, _54, _55, _56, _57, _58, _59, _60, _61, _62, _63, _64,
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_65, _66, _67, _68, _69, _70, _71, _72, _73, _74, _75, _76, _77, _78, _79, _80,
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_81, _82, _83, _84, _85, _86, _87, _88, _89, _90, _91, _92, _93, _94, _95, _96,
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_97, _98, _99, _100, _101, _102, _103, _104, _105, _106, _107, _108, _109, _110, _111, _112,
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_113, _114, _115, _116, _117, _118, _119, _120, _121, _122, _123, _124, _125, _126, _127, _128,
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_129, _130, _131, _132, _133, _134, _135, _136, _137, _138, _139, _140, _141, _142, _143, _144,
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_145, _146, _147, _148, _149, _150, _151, _152, _153, _154, _155, _156, _157, _158, _159, _160,
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_161, _162, _163, _164, _165, _166, _167, _168, _169, _170, _171, _172, _173, _174, _175, _176,
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_177, _178, _179, _180, _181, _182, _183, _184, _185, _186, _187, _188, _189, _190, _191, _192,
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_193, _194, _195, _196, _197, _198, _199, _200, _201, _202, _203, _204, _205, _206, _207, _208,
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_209, _210, _211, _212, _213, _214, _215, _216, _217, _218, _219, _220, _221, _222, _223, _224,
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_225, _226, _227, _228, _229, _230, _231, _232, _233, _234, _235, _236, _237, _238, _239, _240,
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_241, _242, _243, _244, _245, _246, _247, _248, _249, _250, _251, _252, _253, _254,
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}
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#[repr(i8)]
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pub enum X2 {
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_1 = -1, _2 = 0, _3 = 1,
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}
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#[repr(i8)]
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pub enum X3 {
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_1 = -128, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _16,
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_17, _18, _19, _20, _21, _22, _23, _24, _25, _26, _27, _28, _29, _30, _31, _32,
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_33, _34, _35, _36, _37, _38, _39, _40, _41, _42, _43, _44, _45, _46, _47, _48,
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_49, _50, _51, _52, _53, _54, _55, _56, _57, _58, _59, _60, _61, _62, _63, _64,
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_65, _66, _67, _68, _69, _70, _71, _72, _73, _74, _75, _76, _77, _78, _79, _80,
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_81, _82, _83, _84, _85, _86, _87, _88, _89, _90, _91, _92, _93, _94, _95, _96,
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_97, _98, _99, _100, _101, _102, _103, _104, _105, _106, _107, _108, _109, _110, _111, _112,
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_113, _114, _115, _116, _117, _118, _119, _120, _121, _122, _123, _124, _125, _126, _127, _128,
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_129, _130, _131, _132, _133, _134, _135, _136, _137, _138, _139, _140, _141, _142, _143, _144,
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_145, _146, _147, _148, _149, _150, _151, _152, _153, _154, _155, _156, _157, _158, _159, _160,
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_161, _162, _163, _164, _165, _166, _167, _168, _169, _170, _171, _172, _173, _174, _175, _176,
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_177, _178, _179, _180, _181, _182, _183, _184, _185, _186, _187, _188, _189, _190, _191, _192,
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_193, _194, _195, _196, _197, _198, _199, _200, _201, _202, _203, _204, _205, _206, _207, _208,
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_209, _210, _211, _212, _213, _214, _215, _216, _217, _218, _219, _220, _221, _222, _223, _224,
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_225, _226, _227, _228, _229, _230, _231, _232, _233, _234, _235, _236, _237, _238, _239, _240,
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_241, _242, _243, _244, _245, _246, _247, _248, _249, _250, _251, _252, _253, _254,
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}
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#[repr(i8)]
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pub enum X4 {
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_1 = -126, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _16,
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_17, _18, _19, _20, _21, _22, _23, _24, _25, _26, _27, _28, _29, _30, _31, _32,
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_33, _34, _35, _36, _37, _38, _39, _40, _41, _42, _43, _44, _45, _46, _47, _48,
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_49, _50, _51, _52, _53, _54, _55, _56, _57, _58, _59, _60, _61, _62, _63, _64,
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_65, _66, _67, _68, _69, _70, _71, _72, _73, _74, _75, _76, _77, _78, _79, _80,
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_81, _82, _83, _84, _85, _86, _87, _88, _89, _90, _91, _92, _93, _94, _95, _96,
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_97, _98, _99, _100, _101, _102, _103, _104, _105, _106, _107, _108, _109, _110, _111, _112,
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_113, _114, _115, _116, _117, _118, _119, _120, _121, _122, _123, _124, _125, _126, _127, _128,
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_129, _130, _131, _132, _133, _134, _135, _136, _137, _138, _139, _140, _141, _142, _143, _144,
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_145, _146, _147, _148, _149, _150, _151, _152, _153, _154, _155, _156, _157, _158, _159, _160,
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_161, _162, _163, _164, _165, _166, _167, _168, _169, _170, _171, _172, _173, _174, _175, _176,
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_177, _178, _179, _180, _181, _182, _183, _184, _185, _186, _187, _188, _189, _190, _191, _192,
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_193, _194, _195, _196, _197, _198, _199, _200, _201, _202, _203, _204, _205, _206, _207, _208,
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_209, _210, _211, _212, _213, _214, _215, _216, _217, _218, _219, _220, _221, _222, _223, _224,
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_225, _226, _227, _228, _229, _230, _231, _232, _233, _234, _235, _236, _237, _238, _239, _240,
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_241, _242, _243, _244, _245, _246, _247, _248, _249, _250, _251, _252, _253, _254,
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}
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pub enum E<X> {
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A(X),
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B,
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C,
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}
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pub fn match_e<X>(e: E<X>) -> u8 {
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use E::*;
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match e {
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A(_) => 0,
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B => 1,
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C => 2,
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}
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}
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fn main() {
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assert_eq!(match_e(E::A(X1::_1)), 0);
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assert_eq!(match_e(E::A(X1::_2)), 0);
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assert_eq!(match_e(E::A(X1::_254)), 0);
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assert_eq!(match_e(E::<X1>::B), 1);
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assert_eq!(match_e(E::<X1>::C), 2);
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assert_eq!(match_e(E::A(X2::_1)), 0);
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assert_eq!(match_e(E::A(X2::_2)), 0);
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assert_eq!(match_e(E::A(X2::_3)), 0);
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assert_eq!(match_e(E::<X2>::B), 1);
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assert_eq!(match_e(E::<X2>::C), 2);
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assert_eq!(match_e(E::A(X3::_1)), 0);
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assert_eq!(match_e(E::A(X3::_2)), 0);
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assert_eq!(match_e(E::A(X3::_254)), 0);
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assert_eq!(match_e(E::<X3>::B), 1);
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assert_eq!(match_e(E::<X3>::C), 2);
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assert_eq!(match_e(E::A(X4::_1)), 0);
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assert_eq!(match_e(E::A(X4::_2)), 0);
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assert_eq!(match_e(E::A(X4::_254)), 0);
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assert_eq!(match_e(E::<X4>::B), 1);
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assert_eq!(match_e(E::<X4>::C), 2);
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assert_eq!(match_e(E::A(false)), 0);
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assert_eq!(match_e(E::A(true)), 0);
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assert_eq!(match_e(E::<bool>::B), 1);
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assert_eq!(match_e(E::<bool>::C), 2);
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}
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