Another missed optimization.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42546 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt
index aee90a231543c293182374f56d4fa3538c2d9e03..08e219c9b71eafbc8571682e897b2e7434bb1eb5 100644 (file)
--- a/lib/Target/X86/README.txt
+++ b/lib/Target/X86/README.txt
@@ -1239,3 +1239,31 @@ _test:
 
 //===---------------------------------------------------------------------===//
 
+The following code:
+
+LBB3_5:        # bb114.preheader
+       movswl  -68(%ebp), %eax
+       movl    $32, %ecx
+       movl    %ecx, -80(%ebp)
+       subl    %eax, -80(%ebp)
+       movswl  -52(%ebp), %eax
+       movl    %ecx, -84(%ebp)
+       subl    %eax, -84(%ebp)
+       movswl  -70(%ebp), %eax
+       movl    %ecx, -88(%ebp)
+       subl    %eax, -88(%ebp)
+       movswl  -50(%ebp), %eax
+       subl    %eax, %ecx
+       movl    %ecx, -76(%ebp)
+       movswl  -42(%ebp), %eax
+       movl    %eax, -92(%ebp)
+       movswl  -66(%ebp), %eax
+       movl    %eax, -96(%ebp)
+       movw    $0, -98(%ebp)
+
+has redundant subtractions of %eax from a stack slot. However, %ecx doesn't
+change, so we could simply subtract %eax from %ecx first and then use %ecx (or
+vice-versa).
+
+//===---------------------------------------------------------------------===//
+