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Use a 8 bit immediate when possible.

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This fixes pr21529.

llvm-svn: 221700
This commit is contained in:
Rafael Espindola 2014-11-11 19:46:36 +00:00
parent b342691298
commit d10e16c7f3
2 changed files with 29 additions and 2 deletions
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16
lib/Target/X86/X86FrameLowering.cpp
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@ -82,6 +82,17 @@ static unsigned getADDriOpcode(unsigned IsLP64, int64_t Imm) {
}
}
static unsigned getANDriOpcode(bool IsLP64, int64_t Imm) {
if (IsLP64) {
if (isInt<8>(Imm))
return X86::AND64ri8;
return X86::AND64ri32;
}
if (isInt<8>(Imm))
return X86::AND32ri8;
return X86::AND32ri;
}
static unsigned getLEArOpcode(unsigned IsLP64) {
return IsLP64 ? X86::LEA64r : X86::LEA32r;
}
@ -657,11 +668,12 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF) const {
// able to calculate their offsets from the frame pointer).
if (RegInfo->needsStackRealignment(MF)) {
assert(HasFP && "There should be a frame pointer if stack is realigned.");
uint64_t Val = -MaxAlign;
MachineInstr *MI =
BuildMI(MBB, MBBI, DL,
TII.get(Uses64BitFramePtr ? X86::AND64ri32 : X86::AND32ri), StackPtr)
TII.get(getANDriOpcode(Uses64BitFramePtr, Val)), StackPtr)
.addReg(StackPtr)
.addImm(-MaxAlign)
.addImm(Val)
.setMIFlag(MachineInstr::FrameSetup);
// The EFLAGS implicit def is dead.

15
test/CodeGen/X86/pr21529.ll Normal file
View File

@ -0,0 +1,15 @@
; RUN: llc -filetype=obj < %s | llvm-objdump -d - | FileCheck %s
; Test that the direct object emission selects the and variant with 8 bit
; immediate.
; We used to get this wrong when using direct object emission, but not when
; reading assembly.
; CHECK: 48 83 e4 e0 andq $-32, %rsp
target triple = "x86_64-pc-linux"
define void @f() {
%foo = alloca i8, align 32
ret void
}