[llvm] r248786 - Arguments spilled on the stack before a function call may have
Jeroen Ketema via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 29 03:13:00 PDT 2015
Author: jketema
Date: Tue Sep 29 05:12:57 2015
New Revision: 248786
URL: http://llvm.org/viewvc/llvm-project?rev=248786&view=rev
Log:
Arguments spilled on the stack before a function call may have
alignment requirements, for example in the case of vectors.
These requirements are exploited by the code generator by using
move instructions that have similar alignment requirements, e.g.,
movaps on x86.
Although the code generator properly aligns the arguments with
respect to the displacement of the stack pointer it computes,
the displacement itself may cause misalignment. For example if
we have
%3 = load <16 x float>, <16 x float>* %1, align 64
call void @bar(<16 x float> %3, i32 0)
the x86 back-end emits:
movaps 32(%ecx), %xmm2
movaps (%ecx), %xmm0
movaps 16(%ecx), %xmm1
movaps 48(%ecx), %xmm3
subl $20, %esp <-- if %esp was 16-byte aligned before this instruction, it no longer will be afterwards
movaps %xmm3, (%esp) <-- movaps requires 16-byte alignment, while %esp is not aligned as such.
movl $0, 16(%esp)
calll __bar
To solve this, we need to make sure that the computed value with which
the stack pointer is changed is a multiple af the maximal alignment seen
during its computation. With this change we get proper alignment:
subl $32, %esp
movaps %xmm3, (%esp)
Differential Revision: http://reviews.llvm.org/D12337
Added:
llvm/trunk/test/CodeGen/X86/win32-spill-xmm.ll
Modified:
llvm/trunk/include/llvm/CodeGen/CallingConvLower.h
llvm/trunk/lib/CodeGen/CallingConvLower.cpp
llvm/trunk/lib/Target/X86/X86FastISel.cpp
llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
Modified: llvm/trunk/include/llvm/CodeGen/CallingConvLower.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/CallingConvLower.h?rev=248786&r1=248785&r2=248786&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/CallingConvLower.h (original)
+++ llvm/trunk/include/llvm/CodeGen/CallingConvLower.h Tue Sep 29 05:12:57 2015
@@ -201,6 +201,7 @@ private:
LLVMContext &Context;
unsigned StackOffset;
+ unsigned MaxStackArgAlign;
SmallVector<uint32_t, 16> UsedRegs;
SmallVector<CCValAssign, 4> PendingLocs;
@@ -270,7 +271,18 @@ public:
CallingConv::ID getCallingConv() const { return CallingConv; }
bool isVarArg() const { return IsVarArg; }
- unsigned getNextStackOffset() const { return StackOffset; }
+ /// getNextStackOffset - Return the next stack offset such that all stack
+ /// slots satisfy their alignment requirements.
+ unsigned getNextStackOffset() const {
+ return StackOffset;
+ }
+
+ /// getAlignedCallFrameSize - Return the size of the call frame needed to
+ /// be able to store all arguments and such that the alignment requirement
+ /// of each of the arguments is satisfied.
+ unsigned getAlignedCallFrameSize() const {
+ return RoundUpToAlignment(StackOffset, MaxStackArgAlign);
+ }
/// isAllocated - Return true if the specified register (or an alias) is
/// allocated.
@@ -400,9 +412,10 @@ public:
/// and alignment.
unsigned AllocateStack(unsigned Size, unsigned Align) {
assert(Align && ((Align - 1) & Align) == 0); // Align is power of 2.
- StackOffset = ((StackOffset + Align - 1) & ~(Align - 1));
+ StackOffset = RoundUpToAlignment(StackOffset, Align);
unsigned Result = StackOffset;
StackOffset += Size;
+ MaxStackArgAlign = std::max(Align, MaxStackArgAlign);
MF.getFrameInfo()->ensureMaxAlignment(Align);
return Result;
}
Modified: llvm/trunk/lib/CodeGen/CallingConvLower.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/CallingConvLower.cpp?rev=248786&r1=248785&r2=248786&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/CallingConvLower.cpp (original)
+++ llvm/trunk/lib/CodeGen/CallingConvLower.cpp Tue Sep 29 05:12:57 2015
@@ -32,6 +32,7 @@ CCState::CCState(CallingConv::ID CC, boo
CallOrPrologue(Unknown) {
// No stack is used.
StackOffset = 0;
+ MaxStackArgAlign = 1;
clearByValRegsInfo();
UsedRegs.resize((TRI.getNumRegs()+31)/32);
@@ -192,6 +193,7 @@ static bool isValueTypeInRegForCC(Callin
void CCState::getRemainingRegParmsForType(SmallVectorImpl<MCPhysReg> &Regs,
MVT VT, CCAssignFn Fn) {
unsigned SavedStackOffset = StackOffset;
+ unsigned SavedMaxStackArgAlign = MaxStackArgAlign;
unsigned NumLocs = Locs.size();
// Set the 'inreg' flag if it is used for this calling convention.
@@ -223,6 +225,7 @@ void CCState::getRemainingRegParmsForTyp
// as allocated so that future queries don't return the same registers, i.e.
// when i64 and f64 are both passed in GPRs.
StackOffset = SavedStackOffset;
+ MaxStackArgAlign = SavedMaxStackArgAlign;
Locs.resize(NumLocs);
}
Modified: llvm/trunk/lib/Target/X86/X86FastISel.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FastISel.cpp?rev=248786&r1=248785&r2=248786&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86FastISel.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86FastISel.cpp Tue Sep 29 05:12:57 2015
@@ -2906,7 +2906,7 @@ bool X86FastISel::fastLowerCall(CallLowe
CCInfo.AnalyzeCallOperands(OutVTs, OutFlags, CC_X86);
// Get a count of how many bytes are to be pushed on the stack.
- unsigned NumBytes = CCInfo.getNextStackOffset();
+ unsigned NumBytes = CCInfo.getAlignedCallFrameSize();
// Issue CALLSEQ_START
unsigned AdjStackDown = TII.getCallFrameSetupOpcode();
Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=248786&r1=248785&r2=248786&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Tue Sep 29 05:12:57 2015
@@ -3019,7 +3019,7 @@ X86TargetLowering::LowerCall(TargetLower
CCInfo.AnalyzeCallOperands(Outs, CC_X86);
// Get a count of how many bytes are to be pushed on the stack.
- unsigned NumBytes = CCInfo.getNextStackOffset();
+ unsigned NumBytes = CCInfo.getAlignedCallFrameSize();
if (IsSibcall)
// This is a sibcall. The memory operands are available in caller's
// own caller's stack.
Added: llvm/trunk/test/CodeGen/X86/win32-spill-xmm.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/win32-spill-xmm.ll?rev=248786&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/win32-spill-xmm.ll (added)
+++ llvm/trunk/test/CodeGen/X86/win32-spill-xmm.ll Tue Sep 29 05:12:57 2015
@@ -0,0 +1,40 @@
+; RUN: llc -mcpu=generic -mtriple=i686-pc-windows-msvc -mattr=+sse < %s | FileCheck %s
+
+; Check proper alignment of spilled vector
+
+; CHECK-LABEL: spill_ok
+; CHECK: subl $32, %esp
+; CHECK: movaps %xmm3, (%esp)
+; CHECK: movl $0, 16(%esp)
+; CHECK: calll _bar
+define void @spill_ok(i32, <16 x float> *) {
+entry:
+ %2 = alloca i32, i32 %0
+ %3 = load <16 x float>, <16 x float> * %1, align 64
+ tail call void @bar(<16 x float> %3, i32 0) nounwind
+ ret void
+}
+
+declare void @bar(<16 x float> %a, i32 %b)
+
+; Check that proper alignment of spilled vector does not affect vargs
+
+; CHECK-LABEL: vargs_not_affected
+; CHECK: leal 28(%ebp), %eax
+define i32 @vargs_not_affected(<4 x float> %v, i8* %f, ...) {
+entry:
+ %ap = alloca i8*, align 4
+ %0 = bitcast i8** %ap to i8*
+ call void @llvm.va_start(i8* %0)
+ %argp.cur = load i8*, i8** %ap, align 4
+ %argp.next = getelementptr inbounds i8, i8* %argp.cur, i32 4
+ store i8* %argp.next, i8** %ap, align 4
+ %1 = bitcast i8* %argp.cur to i32*
+ %2 = load i32, i32* %1, align 4
+ call void @llvm.va_end(i8* %0)
+ ret i32 %2
+}
+
+declare void @llvm.va_start(i8*)
+
+declare void @llvm.va_end(i8*)
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