Changes in directory llvm/lib/Target/X86:
README.txt updated: 1.99 -> 1.100
---
Log message:
Add a note
---
Diffs of the changes: (+44 -0)
README.txt | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 44 insertions(+)
Index: llvm/lib/Target/X86/README.txt
diff -u llvm/lib/Target/X86/README.txt:1.99 llvm/lib/Target/X86/README.txt:1.100
--- llvm/lib/Target/X86/README.txt:1.99 Thu Apr 27 03:31:33 2006
+++ llvm/lib/Target/X86/README.txt Thu Apr 27 16:40:57 2006
@@ -1144,3 +1144,47 @@
ret
since paddw is commutative.
+
+//===---------------------------------------------------------------------===//
+
+This testcase:
+
+%G1 = weak global <4 x float> zeroinitializer ; <<4 x float>*>
[#uses=1]
+%G2 = weak global <4 x float> zeroinitializer ; <<4 x float>*>
[#uses=1]
+%G3 = weak global <4 x float> zeroinitializer ; <<4 x float>*>
[#uses=1]
+%G4 = weak global <4 x float> zeroinitializer ; <<4 x float>*>
[#uses=1]
+
+implementation ; Functions:
+
+void %test() {
+ %tmp = load <4 x float>* %G1 ; <<4 x float>> [#uses=2]
+ %tmp2 = load <4 x float>* %G2 ; <<4 x float>> [#uses=2]
+ %tmp135 = shufflevector <4 x float> %tmp, <4 x float> %tmp2, <4 x
uint> < uint 0, uint 4, uint 1, uint 5 > ; <<4 x float>> [#uses=1]
+ store <4 x float> %tmp135, <4 x float>* %G3
+ %tmp293 = shufflevector <4 x float> %tmp, <4 x float> %tmp2, <4 x
uint> < uint 1, uint undef, uint 3, uint 4 > ; <<4 x float>> [#uses=1]
+ store <4 x float> %tmp293, <4 x float>* %G4
+ ret void
+}
+
+Compiles (llc -march=x86 -mcpu=yonah -relocation-model=static) to:
+
+_test:
+ movaps _G2, %xmm0
+ movaps _G1, %xmm1
+ movaps %xmm1, %xmm2
+2) shufps $3, %xmm0, %xmm2
+ movaps %xmm1, %xmm3
+2) shufps $1, %xmm0, %xmm3
+1) unpcklps %xmm0, %xmm1
+2) shufps $128, %xmm2, %xmm3
+1) movaps %xmm1, _G3
+ movaps %xmm3, _G4
+ ret
+
+The 1) marked instructions could be scheduled better for reduced register
+pressure. The scheduling issue is more pronounced without -static.
+
+The 2) marked instructions are the lowered form of the 1,undef,3,4
+shufflevector. It seems that there should be a better way to do it :)
+
+
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