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[X86] Call frame optimization - allow stack-relative movs to be folded into a push

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Since we track esp precisely, there's no reason not to allow this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228924 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Kuperstein 2015-02-12 14:17:35 +00:00
parent 44926033f6
commit fb107d8bf0
2 changed files with 11 additions and 17 deletions
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6
lib/Target/X86/X86CallFrameOptimization.cpp
View File

@ -469,12 +469,6 @@ MachineInstr *X86CallFrameOptimization::canFoldIntoRegPush(
DefMI->getParent() != FrameSetup->getParent())
return nullptr;
// Be careful with movs that load from a stack slot, since it may get
// resolved incorrectly.
// TODO: Again, we already have the infrastructure, so this should work.
if (!DefMI->getOperand(1).isReg())
return nullptr;
// Now, make sure everything else up until the ADJCALLSTACK is a sequence
// of MOVs. To be less conservative would require duplicating a lot of the
// logic from PeepholeOptimizer.

22
test/CodeGen/X86/movtopush.ll
View File

@ -103,7 +103,8 @@ entry:
; NORMAL-NEXT: addl $16, %esp
define void @test3(i32 %k) optsize {
entry:
call void @good(i32 %k, i32 2, i32 3, i32 4)
%f = add i32 %k, 1
call void @good(i32 %f, i32 2, i32 3, i32 4)
ret void
}
@ -200,21 +201,20 @@ entry:
ret void
}
; But we don't want to fold stack-relative loads into the push,
; because the offset will be wrong
; Fold stack-relative loads into the push, with correct offset
; In particular, at the second push, %b was at 12(%esp) and
; %a wast at 8(%esp), but the second push bumped %esp, so %a
; is now it at 12(%esp)
; NORMAL-LABEL: test8:
; NORMAL-NOT: subl {{.*}} %esp
; NORMAL: movl 4(%esp), [[EAX:%e..]]
; NORMAL-NEXT: pushl $4
; NORMAL-NEXT: pushl [[EAX]]
; NORMAL-NEXT: pushl $2
; NORMAL: pushl $4
; NORMAL-NEXT: pushl 12(%esp)
; NORMAL-NEXT: pushl 12(%esp)
; NORMAL-NEXT: pushl $1
; NORMAL-NEXT: call
; NORMAL-NEXT: addl $16, %esp
define void @test8(i32* %ptr) optsize {
define void @test8(i32 %a, i32 %b) optsize {
entry:
%val = ptrtoint i32* %ptr to i32
call void @good(i32 1, i32 2, i32 %val, i32 4)
call void @good(i32 1, i32 %a, i32 %b, i32 4)
ret void
}