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Even if we don't have 7 bytes of stack space we may need to save and 

restore the stack pointer from the frame pointer on thumbv6.

Fixes rdar://8819685

llvm-svn: 123196
This commit is contained in:
Eric Christopher 2011-01-11 00:16:04 +00:00
parent bd4520b535
commit 3904343c68
2 changed files with 48 additions and 1 deletions
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9
llvm/lib/Target/ARM/Thumb1FrameLowering.cpp
View File

@ -156,6 +156,12 @@ void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const {
// to reference locals.
if (RegInfo->hasBasePointer(MF))
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2gpr), BasePtr).addReg(ARM::SP);
// If the frame has variable sized objects then the epilogue must restore
// the sp from fp. We can assume there's an FP here since hasFP already
// checks for hasVarSizedObjects.
if (MFI->hasVarSizedObjects())
AFI->setShouldRestoreSPFromFP(true);
}
static bool isCalleeSavedRegister(unsigned Reg, const unsigned *CSRegs) {
@ -221,7 +227,8 @@ void Thumb1FrameLowering::emitEpilogue(MachineFunction &MF,
if (AFI->shouldRestoreSPFromFP()) {
NumBytes = AFI->getFramePtrSpillOffset() - NumBytes;
// Reset SP based on frame pointer only if the stack frame extends beyond
// frame pointer stack slot or target is ELF and the function has FP.
// frame pointer stack slot, the target is ELF and the function has FP, or
// the target uses var sized objects.
if (NumBytes) {
assert(MF.getRegInfo().isPhysRegUsed(ARM::R4) &&
"No scratch register to restore SP from FP!");

40
llvm/test/CodeGen/ARM/thumb1-varalloc.ll Normal file
View File

@ -0,0 +1,40 @@
; RUN: llc < %s -mtriple=thumbv6-apple-darwin | FileCheck %s
; rdar://8819685
@__bar = external hidden global i8*
@__baz = external hidden global i8*
define i8* @_foo() {
entry:
; CHECK: foo:
%size = alloca i32, align 4
%0 = load i8** @__bar, align 4
%1 = icmp eq i8* %0, null
br i1 %1, label %bb1, label %bb3
bb1:
store i32 1026, i32* %size, align 4
%2 = alloca [1026 x i8], align 1
; CHECK: mov r0, sp
; CHECK: adds r4, r0, r4
%3 = getelementptr inbounds [1026 x i8]* %2, i32 0, i32 0
%4 = call i32 @_called_func(i8* %3, i32* %size) nounwind
%5 = icmp eq i32 %4, 0
br i1 %5, label %bb2, label %bb3
bb2:
%6 = call i8* @strdup(i8* %3) nounwind
store i8* %6, i8** @__baz, align 4
br label %bb3
bb3:
%.0 = phi i8* [ %0, %entry ], [ %6, %bb2 ], [ %3, %bb1 ]
; CHECK: subs r4, #5
; CHECK-NEXT: mov sp, r4
; CHECK-NEXT: pop {r4, r5, r6, r7, pc}
ret i8* %.0
}
declare noalias i8* @strdup(i8* nocapture) nounwind
declare i32 @_called_func(i8*, i32*) nounwind