X86: do not fold load instructions such as [V]MOVS[S|D] to other instructions

when the destination register is wider than the memory load.

These load instructions load from m32 or m64 and set the upper bits to zero,
while the folded instructions may accept m128.

rdar://12721174

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168710 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index 5a99ff004d4840093509ccd8d7f96ea45c816f0c..4e31af14eb6a30c7d1769ca968b652be00ab4f32 100644 (file)
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -3982,6 +3982,21 @@ MachineInstr* X86InstrInfo::foldMemoryOperandImpl(MachineFunction &MF,
     break;
   }
   default: {
+    if ((LoadMI->getOpcode() == X86::MOVSSrm ||
+         LoadMI->getOpcode() == X86::VMOVSSrm) &&
+        MF.getRegInfo().getRegClass(LoadMI->getOperand(0).getReg())->getSize()
+          > 4)
+      // These instructions only load 32 bits, we can't fold them if the
+      // destination register is wider than 32 bits (4 bytes).
+      return NULL;
+    if ((LoadMI->getOpcode() == X86::MOVSDrm ||
+         LoadMI->getOpcode() == X86::VMOVSDrm) &&
+        MF.getRegInfo().getRegClass(LoadMI->getOperand(0).getReg())->getSize()
+          > 8)
+      // These instructions only load 64 bits, we can't fold them if the
+      // destination register is wider than 64 bits (8 bytes).
+      return NULL;
+
     // Folding a normal load. Just copy the load's address operands.
     unsigned NumOps = LoadMI->getDesc().getNumOperands();
     for (unsigned i = NumOps - X86::AddrNumOperands; i != NumOps; ++i)

diff --git a/test/CodeGen/X86/fold-load-vec.ll b/test/CodeGen/X86/fold-load-vec.ll
new file mode 100644 (file)
index 0000000..c1756d5
--- /dev/null
+++ b/test/CodeGen/X86/fold-load-vec.ll
@@ -0,0 +1,39 @@
+; RUN: llc < %s -march=x86-64 -mcpu=corei7 -mattr=+sse41 | FileCheck %s
+
+; rdar://12721174
+; We should not fold movss into pshufd since pshufd expects m128 while movss
+; loads from m32.
+define void @sample_test(<4 x float>* %source, <2 x float>* %dest) nounwind {
+; CHECK: sample_test
+; CHECK: movss
+; CHECK: pshufd
+entry:
+  %source.addr = alloca <4 x float>*, align 8
+  %dest.addr = alloca <2 x float>*, align 8
+  %tmp = alloca <2 x float>, align 8
+  store <4 x float>* %source, <4 x float>** %source.addr, align 8
+  store <2 x float>* %dest, <2 x float>** %dest.addr, align 8
+  store <2 x float> zeroinitializer, <2 x float>* %tmp, align 8
+  %0 = load <4 x float>** %source.addr, align 8
+  %arrayidx = getelementptr inbounds <4 x float>* %0, i64 0
+  %1 = load <4 x float>* %arrayidx, align 16
+  %2 = extractelement <4 x float> %1, i32 0
+  %3 = load <2 x float>* %tmp, align 8
+  %4 = insertelement <2 x float> %3, float %2, i32 1
+  store <2 x float> %4, <2 x float>* %tmp, align 8
+  %5 = load <2 x float>* %tmp, align 8
+  %6 = load <2 x float>** %dest.addr, align 8
+  %arrayidx1 = getelementptr inbounds <2 x float>* %6, i64 0
+  store <2 x float> %5, <2 x float>* %arrayidx1, align 8
+  %7 = load <2 x float>** %dest.addr, align 8
+  %arrayidx2 = getelementptr inbounds <2 x float>* %7, i64 0
+  %8 = load <2 x float>* %arrayidx2, align 8
+  %vecext = extractelement <2 x float> %8, i32 0
+  %9 = load <2 x float>** %dest.addr, align 8
+  %arrayidx3 = getelementptr inbounds <2 x float>* %9, i64 0
+  %10 = load <2 x float>* %arrayidx3, align 8
+  %vecext4 = extractelement <2 x float> %10, i32 1
+  call void @ext(float %vecext, float %vecext4)
+  ret void
+}
+declare void @ext(float, float)