[llvm-commits] [llvm] r95649 - /llvm/trunk/lib/Target/X86/README-SSE.txt

[Chris Lattner]

Author: lattner
Date: Mon Feb  8 23:45:29 2010
New Revision: 95649

URL: http://llvm.org/viewvc/llvm-project?rev=95649&view=rev
Log:
add a note from PR6194

Modified:
    llvm/trunk/lib/Target/X86/README-SSE.txt

Modified: llvm/trunk/lib/Target/X86/README-SSE.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/README-SSE.txt?rev=95649&r1=95648&r2=95649&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/README-SSE.txt (original)
+++ llvm/trunk/lib/Target/X86/README-SSE.txt Mon Feb  8 23:45:29 2010
@@ -954,3 +954,36 @@
 
 //===---------------------------------------------------------------------===//
 
+This IR (from PR6194):
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-apple-darwin10.0.0"
+
+%0 = type { double, double }
+%struct.float3 = type { float, float, float }
+
+define void @test(%0, %struct.float3* nocapture %res) nounwind noinline ssp {
+entry:
+  %tmp18 = extractvalue %0 %0, 0                  ; <double> [#uses=1]
+  %tmp19 = bitcast double %tmp18 to i64           ; <i64> [#uses=1]
+  %tmp20 = zext i64 %tmp19 to i128                ; <i128> [#uses=1]
+  %tmp10 = lshr i128 %tmp20, 32                   ; <i128> [#uses=1]
+  %tmp11 = trunc i128 %tmp10 to i32               ; <i32> [#uses=1]
+  %tmp12 = bitcast i32 %tmp11 to float            ; <float> [#uses=1]
+  %tmp5 = getelementptr inbounds %struct.float3* %res, i64 0, i32 1 ; <float*> [#uses=1]
+  store float %tmp12, float* %tmp5
+  ret void
+}
+
+Compiles to:
+
+_test:                                  ## @test
+	movd	%xmm0, %rax
+	shrq	$32, %rax
+	movl	%eax, 4(%rdi)
+	ret
+
+This would be better kept in the SSE unit by treating XMM0 as a 4xfloat and
+doing a shuffle from v[1] to v[0] then a float store.
+
+//===---------------------------------------------------------------------===//