In Thumb2 mode, lower frame indix references to:
add <rd>, sp, #<imm8>
ldr <rd>, [sp, #<imm8>]
When the offset from sp is multiple of 4 and in range of 0-1020.
This saves code size by utilizing 16-bit instructions.
rdar://9321541
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129971 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMFrameLowering.cpp b/lib/Target/ARM/ARMFrameLowering.cpp
index c99259d..e2e95d4 100644
--- a/lib/Target/ARM/ARMFrameLowering.cpp
+++ b/lib/Target/ARM/ARMFrameLowering.cpp
@@ -445,8 +445,7 @@
int
ARMFrameLowering::ResolveFrameIndexReference(const MachineFunction &MF,
- int FI,
- unsigned &FrameReg,
+ int FI, unsigned &FrameReg,
int SPAdj) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
const ARMBaseRegisterInfo *RegInfo =
@@ -490,19 +489,23 @@
return FPOffset;
} else if (MFI->hasVarSizedObjects()) {
assert(RegInfo->hasBasePointer(MF) && "missing base pointer!");
- // Try to use the frame pointer if we can, else use the base pointer
- // since it's available. This is handy for the emergency spill slot, in
- // particular.
if (AFI->isThumb2Function()) {
+ // Try to use the frame pointer if we can, else use the base pointer
+ // since it's available. This is handy for the emergency spill slot, in
+ // particular.
if (FPOffset >= -255 && FPOffset < 0) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
- } else
- FrameReg = RegInfo->getBaseRegister();
+ }
} else if (AFI->isThumb2Function()) {
+ // Use add <rd>, sp, #<imm8>
+ // ldr <rd>, [sp, #<imm8>]
+ // if at all possible to save space.
+ if (Offset >= 0 && (Offset & 3) == 0 && Offset <= 1020)
+ return Offset;
// In Thumb2 mode, the negative offset is very limited. Try to avoid
- // out of range references.
+ // out of range references. ldr <rt>,[<rn>, #-<imm8>]
if (FPOffset >= -255 && FPOffset < 0) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
diff --git a/lib/Target/ARM/ARMFrameLowering.h b/lib/Target/ARM/ARMFrameLowering.h
index a7b7f15..61bb8af 100644
--- a/lib/Target/ARM/ARMFrameLowering.h
+++ b/lib/Target/ARM/ARMFrameLowering.h
@@ -51,7 +51,8 @@
bool canSimplifyCallFramePseudos(const MachineFunction &MF) const;
int getFrameIndexReference(const MachineFunction &MF, int FI,
unsigned &FrameReg) const;
- int ResolveFrameIndexReference(const MachineFunction &MF, int FI,
+ int ResolveFrameIndexReference(const MachineFunction &MF,
+ int FI,
unsigned &FrameReg, int SPAdj) const;
int getFrameIndexOffset(const MachineFunction &MF, int FI) const;
diff --git a/test/CodeGen/Thumb2/2011-04-21-FILoweringBug.ll b/test/CodeGen/Thumb2/2011-04-21-FILoweringBug.ll
new file mode 100644
index 0000000..604a352
--- /dev/null
+++ b/test/CodeGen/Thumb2/2011-04-21-FILoweringBug.ll
@@ -0,0 +1,23 @@
+; RUN: llc < %s -mtriple=thumbv7-apple-darwin | FileCheck %s
+
+; Use sp, #imm to lower frame indices when the offset is multiple of 4
+; and in the range of 0-1020. This saves code size by utilizing
+; 16-bit instructions.
+; rdar://9321541
+
+define i32 @t() nounwind {
+entry:
+; CHECK: t:
+; CHECK: sub sp, #12
+; CHECK-NOT: sub
+; CHECK: add r0, sp, #4
+; CHECK: add r1, sp, #8
+; CHECK: mov r2, sp
+ %size = alloca i32, align 4
+ %count = alloca i32, align 4
+ %index = alloca i32, align 4
+ %0 = call i32 @foo(i32* %count, i32* %size, i32* %index) nounwind
+ ret i32 %0
+}
+
+declare i32 @foo(i32*, i32*, i32*)