we compile multiply-by-constant into horrible code. Doesn't sse4 have some

instruction for doing this?

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51473 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/README-SSE.txt b/lib/Target/X86/README-SSE.txt
index 61649726e3816365b6dd2e9dbc820ef771e1c35c..f200cbf11a4bc9ad63763fdddd2c7960222ad86c 100644 (file)
--- a/lib/Target/X86/README-SSE.txt
+++ b/lib/Target/X86/README-SSE.txt
@@ -807,3 +807,41 @@ foo1:
 
 //===---------------------------------------------------------------------===//
 
+We compile vector multiply-by-constant into poor code:
+
+define <4 x i32> @f(<4 x i32> %i) nounwind  {
+       %A = mul <4 x i32> %i, < i32 10, i32 10, i32 10, i32 10 >
+       ret <4 x i32> %A
+}
+
+Compiles into:
+
+LCPI1_0:                                       ##  <4 x i32>
+       .long   10
+       .long   10
+       .long   10
+       .long   10
+       .text
+       .align  4,0x90
+       .globl  _f
+_f:
+       pshufd  $3, %xmm0, %xmm1
+       movd    %xmm1, %eax
+       imull   LCPI1_0+12, %eax
+       movd    %eax, %xmm1
+       pshufd  $1, %xmm0, %xmm2
+       movd    %xmm2, %eax
+       imull   LCPI1_0+4, %eax
+       movd    %eax, %xmm2
+       punpckldq       %xmm1, %xmm2
+       movd    %xmm0, %eax
+       imull   LCPI1_0, %eax
+       movd    %eax, %xmm1
+       movhlps %xmm0, %xmm0
+       movd    %xmm0, %eax
+       imull   LCPI1_0+8, %eax
+       movd    %eax, %xmm0
+       punpckldq       %xmm0, %xmm1
+       movaps  %xmm1, %xmm0
+       punpckldq       %xmm2, %xmm0
+       ret