Changes in directory llvm/lib/Target/X86:
README.txt updated: 1.102 -> 1.103
---
Log message:
Another bad case I noticed
---
Diffs of the changes: (+37 -0)
README.txt | 37 +++++++++++++++++++++++++++++++++++++
1 files changed, 37 insertions(+)
Index: llvm/lib/Target/X86/README.txt
diff -u llvm/lib/Target/X86/README.txt:1.102
llvm/lib/Target/X86/README.txt:1.103
--- llvm/lib/Target/X86/README.txt:1.102 Mon May 8 16:24:21 2006
+++ llvm/lib/Target/X86/README.txt Mon May 8 16:39:45 2006
@@ -1176,3 +1176,40 @@
The former can also be used when the two-addressy nature of the 'and' would
require a copy to be inserted (in X86InstrInfo::convertToThreeAddress).
+//===---------------------------------------------------------------------===//
+
+This code generates ugly code, probably due to costs being off or something:
+
+void %test(float* %P, <4 x float>* %P2 ) {
+ %xFloat0.688 = load float* %P
+ %loadVector37.712 = load <4 x float>* %P2
+ %inFloat3.713 = insertelement <4 x float> %loadVector37.712, float
0.000000e+00, uint 3
+ store <4 x float> %inFloat3.713, <4 x float>* %P2
+ ret void
+}
+
+Generates:
+
+_test:
+ pxor %xmm0, %xmm0
+ movd %xmm0, %eax ;; EAX = 0!
+ movl 8(%esp), %ecx
+ movaps (%ecx), %xmm0
+ pinsrw $6, %eax, %xmm0
+ shrl $16, %eax ;; EAX = 0 again!
+ pinsrw $7, %eax, %xmm0
+ movaps %xmm0, (%ecx)
+ ret
+
+It would be better to generate:
+
+_test:
+ movl 8(%esp), %ecx
+ movaps (%ecx), %xmm0
+ xor %eax, %eax
+ pinsrw $6, %eax, %xmm0
+ pinsrw $7, %eax, %xmm0
+ movaps %xmm0, (%ecx)
+ ret
+
+or use pxor (to make a zero vector) and shuffle (to insert it).
_______________________________________________
llvm-commits mailing list
llvm-commits@cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
