diff options
| -rw-r--r-- | llvm/lib/Target/X86/X86InstrInfo.cpp | 16 | ||||
| -rw-r--r-- | llvm/test/CodeGen/X86/cmpxchg-clobber-flags.ll | 43 | ||||
| -rw-r--r-- | llvm/test/CodeGen/X86/peephole-na-phys-copy-folding.ll | 8 |
3 files changed, 57 insertions, 10 deletions
diff --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp index 12da3a9319e..e9d36f8ce2f 100644 --- a/llvm/lib/Target/X86/X86InstrInfo.cpp +++ b/llvm/lib/Target/X86/X86InstrInfo.cpp @@ -4412,9 +4412,19 @@ void X86InstrInfo::copyPhysReg(MachineBasicBlock &MBB, int Pop = is64 ? X86::POP64r : X86::POP32r; int AX = is64 ? X86::RAX : X86::EAX; - bool AXDead = (Reg == AX) || - (MachineBasicBlock::LQR_Dead == - MBB.computeRegisterLiveness(&getRegisterInfo(), AX, MI)); + bool AXDead = (Reg == AX); + // FIXME: The above could figure out that AX is dead in more cases with: + // || (MachineBasicBlock::LQR_Dead == + // MBB.computeRegisterLiveness(&getRegisterInfo(), AX, MI)); + // + // Unfortunately this is slightly broken, see PR24535 and the likely + // related PR25033 PR24991 PR24992 PR25201. These issues seem to + // showcase sub-register / super-register confusion: a previous kill + // of AH but no kill of AL leads computeRegisterLiveness to + // erroneously conclude that AX is dead. + // + // Once fixed, also update cmpxchg-clobber-flags.ll and + // peephole-na-phys-copy-folding.ll. if (!AXDead) BuildMI(MBB, MI, DL, get(Push)).addReg(AX, getKillRegState(true)); diff --git a/llvm/test/CodeGen/X86/cmpxchg-clobber-flags.ll b/llvm/test/CodeGen/X86/cmpxchg-clobber-flags.ll index c129128b5fa..791edba89c4 100644 --- a/llvm/test/CodeGen/X86/cmpxchg-clobber-flags.ll +++ b/llvm/test/CodeGen/X86/cmpxchg-clobber-flags.ll @@ -1,7 +1,14 @@ -; RUN: llc -verify-machineinstrs -mtriple=i386-linux-gnu %s -o - | FileCheck %s -check-prefix=i386 -; RUN: llc -verify-machineinstrs -mtriple=i386-linux-gnu -pre-RA-sched=fast %s -o - | FileCheck %s -check-prefix=i386f -; RUN: llc -verify-machineinstrs -mtriple=x86_64-linux-gnu %s -o - | FileCheck %s -check-prefix=x8664 -; RUN: llc -verify-machineinstrs -mtriple=x86_64-linux-gnu -pre-RA-sched=fast %s -o - | FileCheck %s -check-prefix=x8664 +; RUN: llc -mtriple=i386-linux-gnu %s -o - | FileCheck %s -check-prefix=i386 +; RUN: llc -mtriple=i386-linux-gnu -pre-RA-sched=fast %s -o - | FileCheck %s -check-prefix=i386f +; RUN: llc -mtriple=x86_64-linux-gnu %s -o - | FileCheck %s -check-prefix=x8664 +; RUN: llc -mtriple=x86_64-linux-gnu -pre-RA-sched=fast %s -o - | FileCheck %s -check-prefix=x8664 + +; FIXME: X86InstrInfo::copyPhysReg had code which figured out whether AX was +; live or not to avoid save / restore when it's not needed. See FIXME in +; that function for more details on which the code is currently +; disabled. The extra push/pop are marked below and can be removed once +; the issue is fixed. +; -verify-machineinstrs should also be added back in the RUN lines above. declare i32 @foo() declare i32 @bar(i64) @@ -17,22 +24,34 @@ define i64 @test_intervening_call(i64* %foo, i64 %bar, i64 %baz) { ; i386-NEXT: movl %edx, 4(%esp) ; i386-NEXT: movl %eax, (%esp) ; i386-NEXT: calll bar +; ** FIXME Next line isn't actually necessary. ** +; i386-NEXT: pushl %eax ; i386-NEXT: movl [[FLAGS]], %eax ; i386-NEXT: addb $127, %al ; i386-NEXT: sahf +; ** FIXME Next line isn't actually necessary. ** +; i386-NEXT: popl %eax ; i386-NEXT: jne ; i386f-LABEL: test_intervening_call: ; i386f: cmpxchg8b ; i386f-NEXT: movl %eax, (%esp) ; i386f-NEXT: movl %edx, 4(%esp) +; ** FIXME Next line isn't actually necessary. ** +; i386f-NEXT: pushl %eax ; i386f-NEXT: seto %al ; i386f-NEXT: lahf ; i386f-NEXT: movl %eax, [[FLAGS:%.*]] +; ** FIXME Next line isn't actually necessary. ** +; i386f-NEXT: popl %eax ; i386f-NEXT: calll bar +; ** FIXME Next line isn't actually necessary. ** +; i386f-NEXT: pushl %eax ; i386f-NEXT: movl [[FLAGS]], %eax ; i386f-NEXT: addb $127, %al ; i386f-NEXT: sahf +; ** FIXME Next line isn't actually necessary. ** +; i386f-NEXT: popl %eax ; i386f-NEXT: jne ; x8664-LABEL: test_intervening_call: @@ -44,9 +63,13 @@ define i64 @test_intervening_call(i64* %foo, i64 %bar, i64 %baz) { ; x8664-NEXT: popq %rax ; x8664-NEXT: movq %rax, %rdi ; x8664-NEXT: callq bar +; ** FIXME Next line isn't actually necessary. ** +; x8664-NEXT: pushq %rax ; x8664-NEXT: movq [[FLAGS]], %rax ; x8664-NEXT: addb $127, %al ; x8664-NEXT: sahf +; ** FIXME Next line isn't actually necessary. ** +; x8664-NEXT: popq %rax ; x8664-NEXT: jne %cx = cmpxchg i64* %foo, i64 %bar, i64 %baz seq_cst seq_cst @@ -111,9 +134,13 @@ cond.end: define i32 @test_feed_cmov(i32* %addr, i32 %desired, i32 %new) { ; i386-LABEL: test_feed_cmov: ; i386: cmpxchgl +; ** FIXME Next line isn't actually necessary. ** +; i386-NEXT: pushl %eax ; i386-NEXT: seto %al ; i386-NEXT: lahf ; i386-NEXT: movl %eax, [[FLAGS:%.*]] +; ** FIXME Next line isn't actually necessary. ** +; i386-NEXT: popl %eax ; i386-NEXT: calll foo ; i386-NEXT: pushl %eax ; i386-NEXT: movl [[FLAGS]], %eax @@ -123,9 +150,13 @@ define i32 @test_feed_cmov(i32* %addr, i32 %desired, i32 %new) { ; i386f-LABEL: test_feed_cmov: ; i386f: cmpxchgl +; ** FIXME Next line isn't actually necessary. ** +; i386f-NEXT: pushl %eax ; i386f-NEXT: seto %al ; i386f-NEXT: lahf ; i386f-NEXT: movl %eax, [[FLAGS:%.*]] +; ** FIXME Next line isn't actually necessary. ** +; i386f-NEXT: popl %eax ; i386f-NEXT: calll foo ; i386f-NEXT: pushl %eax ; i386f-NEXT: movl [[FLAGS]], %eax @@ -135,9 +166,13 @@ define i32 @test_feed_cmov(i32* %addr, i32 %desired, i32 %new) { ; x8664-LABEL: test_feed_cmov: ; x8664: cmpxchgl +; ** FIXME Next line isn't actually necessary. ** +; x8664: pushq %rax ; x8664: seto %al ; x8664-NEXT: lahf ; x8664-NEXT: movq %rax, [[FLAGS:%.*]] +; ** FIXME Next line isn't actually necessary. ** +; x8664-NEXT: popq %rax ; x8664-NEXT: callq foo ; x8664-NEXT: pushq %rax ; x8664-NEXT: movq [[FLAGS]], %rax diff --git a/llvm/test/CodeGen/X86/peephole-na-phys-copy-folding.ll b/llvm/test/CodeGen/X86/peephole-na-phys-copy-folding.ll index 438bf8ddf4c..891a925611c 100644 --- a/llvm/test/CodeGen/X86/peephole-na-phys-copy-folding.ll +++ b/llvm/test/CodeGen/X86/peephole-na-phys-copy-folding.ll @@ -1,5 +1,7 @@ -; RUN: llc -verify-machineinstrs -mtriple=i386-linux-gnu %s -o - | FileCheck %s -; RUN: llc -verify-machineinstrs -mtriple=x86_64-linux-gnu %s -o - | FileCheck %s +; RUN: llc -mtriple=i386-linux-gnu %s -o - | FileCheck %s +; RUN: llc -mtriple=x86_64-linux-gnu %s -o - | FileCheck %s + +; FIXME Add -verify-machineinstrs back when PR24535 is fixed. ; The peephole optimizer can elide some physical register copies such as ; EFLAGS. Make sure the flags are used directly, instead of needlessly using @@ -137,7 +139,7 @@ f: ; CHECK-LABEL: test_two_live_flags: ; CHECK: cmpxchg -; CHECK-NEXT: seto %al +; CHECK: seto %al ; CHECK-NEXT: lahf ; Save result of the first cmpxchg into D. ; CHECK-NEXT: mov{{[lq]}} %[[AX:[er]ax]], %[[D:[re]d[xi]]] |
