Author: lattner
Date: Sat Jan 26 13:45:50 2008
New Revision: 46401
URL: http://llvm.org/viewvc/llvm-project?rev=46401&view=rev
Log:
Infer alignment of loads and increase their alignment when we can tell they are
from the stack. This allows us to compile stack-align.ll to:
_test:
movsd LCPI1_0, %xmm0
movapd %xmm0, %xmm1
*** andpd 4(%esp), %xmm1
andpd _G, %xmm0
addsd %xmm1, %xmm0
movl 20(%esp), %eax
movsd %xmm0, (%eax)
ret
instead of:
_test:
movsd LCPI1_0, %xmm0
** movsd 4(%esp), %xmm1
** andpd %xmm0, %xmm1
andpd _G, %xmm0
addsd %xmm1, %xmm0
movl 20(%esp), %eax
movsd %xmm0, (%eax)
ret
Added:
llvm/trunk/test/CodeGen/X86/stack-align.ll
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=46401&r1=46400&r2=46401&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Sat Jan 26 13:45:50 2008
@@ -18,6 +18,7 @@
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
@@ -4073,13 +4074,41 @@
static unsigned InferAlignment(SDOperand Ptr, SelectionDAG &DAG) {
// If this is a direct reference to a stack slot, use information about the
// stack slot's alignment.
+ int FrameIdx = 1 << 31;
+ int64_t FrameOffset = 0;
if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Ptr)) {
- return DAG.getMachineFunction().getFrameInfo()->
- getObjectAlignment(FI->getIndex());
+ FrameIdx = FI->getIndex();
+ } else if (Ptr.getOpcode() == ISD::ADD &&
+ isa<ConstantSDNode>(Ptr.getOperand(1)) &&
+ isa<FrameIndexSDNode>(Ptr.getOperand(0))) {
+ FrameIdx = cast<FrameIndexSDNode>(Ptr.getOperand(0))->getIndex();
+ FrameOffset = Ptr.getConstantOperandVal(1);
+ }
+
+ if (FrameIdx != (1 << 31)) {
+ // FIXME: Handle FI+CST.
+ const MachineFrameInfo &MFI = *DAG.getMachineFunction().getFrameInfo();
+ if (MFI.isFixedObjectIndex(FrameIdx)) {
+ int64_t ObjectOffset = MFI.getObjectOffset(FrameIdx);
+
+ // The alignment of the frame index can be determined from its offset
from
+ // the incoming frame position. If the frame object is at offset 32 and
+ // the stack is guaranteed to be 16-byte aligned, then we know that the
+ // object is 16-byte aligned.
+ unsigned StackAlign =
DAG.getTarget().getFrameInfo()->getStackAlignment();
+ unsigned Align = MinAlign(ObjectOffset, StackAlign);
+
+ // Finally, the frame object itself may have a known alignment. Factor
+ // the alignment + offset into a new alignment. For example, if we know
+ // the FI is 8 byte aligned, but the pointer is 4 off, we really have a
+ // 4-byte alignment of the resultant pointer. Likewise align 4 + 4-byte
+ // offset = 4-byte alignment, align 4 + 1-byte offset = align 1, etc.
+ unsigned FIInfoAlign = MinAlign(MFI.getObjectAlignment(FrameIdx),
+ FrameOffset);
+ return std::max(Align, FIInfoAlign);
+ }
}
- // FIXME: Handle FI+CST.
-
return 0;
}
Added: llvm/trunk/test/CodeGen/X86/stack-align.ll
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/stack-align.ll?rev=46401&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/stack-align.ll (added)
+++ llvm/trunk/test/CodeGen/X86/stack-align.ll Sat Jan 26 13:45:50 2008
@@ -0,0 +1,22 @@
+; RUN: llvm-as < %s | llc -relocation-model=static -mcpu=yonah | grep
{andpd.*4(%esp), %xmm}
+
+; The double argument is at 4(esp) which is 16-byte aligned, allowing us to
+; fold the load into the andpd.
+
+target datalayout =
"e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i686-apple-darwin8"
[EMAIL PROTECTED] = external global double
+
+define void @test({ double, double }* byval %z, double* %P) {
+entry:
+ %tmp = getelementptr { double, double }* %z, i32 0, i32 0
; <double*> [#uses=1]
+ %tmp1 = load double* %tmp, align 8 ; <double> [#uses=1]
+ %tmp2 = tail call double @fabs( double %tmp1 ) ; <double>
[#uses=1]
+ %tmp3 = load double* @G, align 16 ; <double> [#uses=1]
+ %tmp4 = tail call double @fabs( double %tmp3 ) ; <double>
[#uses=1]
+ %tmp6 = add double %tmp4, %tmp2 ; <double> [#uses=1]
+ store double %tmp6, double* %P, align 8
+ ret void
+}
+
+declare double @fabs(double)
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