[llvm-commits] [llvm] r58483 - in /llvm/trunk: lib/Target/X86/X86ISelLowering.cpp test/CodeGen/X86/extractps.ll

[Dan Gohman]

Author: djg
Date: Thu Oct 30 19:57:24 2008
New Revision: 58483

URL: http://llvm.org/viewvc/llvm-project?rev=58483&view=rev
Log:
Use MOVSSmr instead of EXTRACTPSmr in the case of extracting
vector element 0 for a store, as it's smaller and faster.

Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
    llvm/trunk/test/CodeGen/X86/extractps.ll

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=58483&r1=58482&r2=58483&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Thu Oct 30 19:57:24 2008
@@ -4194,11 +4194,15 @@
   } else if (VT == MVT::f32) {
     // EXTRACTPS outputs to a GPR32 register which will require a movd to copy
     // the result back to FR32 register. It's only worth matching if the
-    // result has a single use which is a store or a bitcast to i32.
+    // result has a single use which is a store or a bitcast to i32.  And in
+    // the case of a store, it's not worth it if the index is a constant 0,
+    // because a MOVSSmr can be used instead, which is smaller and faster.
     if (!Op.hasOneUse())
       return SDValue();
     SDNode *User = *Op.getNode()->use_begin();
-    if (User->getOpcode() != ISD::STORE &&
+    if ((User->getOpcode() != ISD::STORE ||
+         (isa<ConstantSDNode>(Op.getOperand(1)) &&
+          cast<ConstantSDNode>(Op.getOperand(1))->isNullValue())) &&
         (User->getOpcode() != ISD::BIT_CONVERT ||
          User->getValueType(0) != MVT::i32))
       return SDValue();

Modified: llvm/trunk/test/CodeGen/X86/extractps.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/extractps.ll?rev=58483&r1=58482&r2=58483&view=diff

==============================================================================
--- llvm/trunk/test/CodeGen/X86/extractps.ll (original)
+++ llvm/trunk/test/CodeGen/X86/extractps.ll Thu Oct 30 19:57:24 2008
@@ -1,7 +1,7 @@
 ; RUN: llvm-as < %s | llc -march=x86 -mcpu=penryn > %t
 ; RUN: not grep movd %t
-; RUN: not grep movss %t
-; RUN: grep {extractps	\\\$0, %xmm0, } %t
+; RUN: grep {movss	%xmm} %t | count 1
+; RUN: grep {extractps	\\\$1, %xmm0, } %t | count 1
 ; PR2647
 
 external global float, align 16         ; <float*>:0 [#uses=2]
@@ -14,6 +14,14 @@
         store float %4, float* @0, align 16
         ret void
 }
+define internal void @""() nounwind {
+        load float* @0, align 16                ; <float>:1 [#uses=1]
+        insertelement <4 x float> undef, float %1, i32 1                ; <<4 x float>>:2 [#uses=1]
+        call <4 x float> @llvm.x86.sse.rsqrt.ss( <4 x float> %2 )              ; <<4 x float>>:3 [#uses=1]
+        extractelement <4 x float> %3, i32 1            ; <float>:4 [#uses=1]
+        store float %4, float* @0, align 16
+        ret void
+}
 
 declare <4 x float> @llvm.x86.sse.rsqrt.ss(<4 x float>) nounwind readnone