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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28383 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt
index 1ace55927c4ab6a17b190d86bf215a33361e1570..05dc535a7b27064e88dbdf2f4d7995a02de79a16 100644 (file)
--- a/lib/Target/X86/README.txt
+++ b/lib/Target/X86/README.txt
@@ -380,6 +380,21 @@ bool %test(int %X) {
 
 This may just be a matter of using 'test' to write bigger patterns for X86cmp.
 
+An important case is comparison against zero:
+
+if (X == 0) ...
+
+instead of:
+
+       cmpl $0, %eax
+       je LBB4_2       #cond_next
+
+use:
+       test %eax, %eax
+       jz LBB4_2
+
+which is smaller.
+
 //===---------------------------------------------------------------------===//
 
 SSE should implement 'select_cc' using 'emulated conditional moves' that use