diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Target/X86/README-SSE.txt | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/lib/Target/X86/README-SSE.txt b/lib/Target/X86/README-SSE.txt index 7269fa2..1f5f203 100644 --- a/lib/Target/X86/README-SSE.txt +++ b/lib/Target/X86/README-SSE.txt @@ -814,7 +814,7 @@ define <4 x i32> @f(<4 x i32> %i) nounwind { ret <4 x i32> %A } -Compiles into: +On targets without SSE4.1, this compiles into: LCPI1_0: ## <4 x i32> .long 10 @@ -846,6 +846,11 @@ _f: punpckldq %xmm2, %xmm0 ret +It would be better to synthesize integer vector multiplication by constants +using shifts and adds, pslld and paddd here. And even on targets with SSE4.1, +simple cases such as multiplication by powers of two would be better as +vector shifts than as multiplications. + //===---------------------------------------------------------------------===// We compile this: |