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The red zone consists of 128 bytes beyond the stack pointer so that the allocation of objects in leaf functions doesn't require decrementing rsp. In r255656, we introduced an optimization that would cheaply materialize certain constants via push/pop. Push decrements the stack pointer and stores it's result at what is now the top of the stack. However, this means that using push/pop would encroach on the red zone. PR26023 gives an example where this corrupts an object in the red zone. llvm-svn: 256808
101 lines
2.6 KiB
LLVM
101 lines
2.6 KiB
LLVM
; RUN: llc -mtriple=i686-unknown-linux-gnu -mattr=+cmov %s -o - | FileCheck %s --check-prefix=CHECK32
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; RUN: llc -mtriple=x86_64-unknown-linux-gnu -mattr=+cmov %s -o - | FileCheck %s --check-prefix=CHECK64
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define i32 @one32() optsize {
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entry:
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ret i32 1
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; CHECK32-LABEL: one32
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; CHECK32: xorl %eax, %eax
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; CHECK32-NEXT: incl %eax
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; CHECK32-NEXT: ret
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; FIXME: Figure out the best approach in 64-bit mode.
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; CHECK64-LABEL: one32
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; CHECK64: movl $1, %eax
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; CHECK64-NEXT: retq
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}
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define i32 @minus_one32() optsize {
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entry:
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ret i32 -1
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; CHECK32-LABEL: minus_one32
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; CHECK32: xorl %eax, %eax
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; CHECK32-NEXT: decl %eax
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; CHECK32-NEXT: ret
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}
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define i16 @one16() optsize {
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entry:
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ret i16 1
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; CHECK32-LABEL: one16
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; CHECK32: xorl %eax, %eax
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; CHECK32-NEXT: incl %eax
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; CHECK32-NEXT: retl
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}
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define i16 @minus_one16() optsize {
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entry:
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ret i16 -1
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; CHECK32-LABEL: minus_one16
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; CHECK32: xorl %eax, %eax
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; CHECK32-NEXT: decl %eax
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; CHECK32-NEXT: retl
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}
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define i32 @test_rematerialization() optsize {
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entry:
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; Materialize -1 (thiscall forces it into %ecx).
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tail call x86_thiscallcc void @f(i32 -1)
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; Clobber all registers except %esp, leaving nowhere to store the -1 besides
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; spilling it to the stack.
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tail call void asm sideeffect "", "~{eax},~{ebx},~{ecx},~{edx},~{edi},~{esi},~{ebp},~{dirflag},~{fpsr},~{flags}"()
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; -1 should be re-materialized here instead of getting spilled above.
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ret i32 -1
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; CHECK32-LABEL: test_rematerialization
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; CHECK32: xorl %ecx, %ecx
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; CHECK32-NEXT: decl %ecx
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; CHECK32: calll
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; CHECK32: xorl %eax, %eax
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; CHECK32-NEXT: decl %eax
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; CHECK32-NOT: %eax
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; CHECK32: retl
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}
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define i32 @test_rematerialization2(i32 %x) optsize {
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entry:
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; Materialize -1 (thiscall forces it into %ecx).
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tail call x86_thiscallcc void @f(i32 -1)
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; Clobber all registers except %esp, leaving nowhere to store the -1 besides
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; spilling it to the stack.
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tail call void asm sideeffect "", "~{eax},~{ebx},~{ecx},~{edx},~{edi},~{esi},~{ebp},~{dirflag},~{fpsr},~{flags}"()
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; Define eflags.
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%a = icmp ne i32 %x, 123
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%b = zext i1 %a to i32
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; Cause -1 to be rematerialized right in front of the cmov, which needs eflags.
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; It must therefore not use the xor-dec lowering.
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%c = select i1 %a, i32 %b, i32 -1
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ret i32 %c
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; CHECK32-LABEL: test_rematerialization2
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; CHECK32: xorl %ecx, %ecx
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; CHECK32-NEXT: decl %ecx
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; CHECK32: calll
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; CHECK32: cmpl
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; CHECK32: setne
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; CHECK32-NOT: xorl
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; CHECK32: movl $-1
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; CHECK32: cmov
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; CHECK32: retl
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}
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declare x86_thiscallcc void @f(i32)
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