[llvm-commits] CVS: llvm/lib/Target/X86/README.txt

[Chris Lattner]

Changes in directory llvm/lib/Target/X86:

README.txt updated: 1.166 -> 1.167
---
Log message:

move CodeGen/X86/overlap-add.ll here.


---
Diffs of the changes:  (+27 -0)

 README.txt |   27 +++++++++++++++++++++++++++
 1 files changed, 27 insertions(+)


Index: llvm/lib/Target/X86/README.txt
diff -u llvm/lib/Target/X86/README.txt:1.166 llvm/lib/Target/X86/README.txt:1.167
--- llvm/lib/Target/X86/README.txt:1.166	Mon Apr 16 19:02:37 2007
+++ llvm/lib/Target/X86/README.txt	Sat May  5 17:10:24 2007
@@ -1004,6 +1004,33 @@
         movl %edi, %eax
         ret
 
+Another example is:
+
+;; X's live range extends beyond the shift, so the register allocator
+;; cannot coalesce it with Y.  Because of this, a copy needs to be
+;; emitted before the shift to save the register value before it is
+;; clobbered.  However, this copy is not needed if the register
+;; allocator turns the shift into an LEA.  This also occurs for ADD.
+
+; Check that the shift gets turned into an LEA.
+; RUN: llvm-upgrade < %s | llvm-as | llc -march=x86 -x86-asm-syntax=intel | \
+; RUN:   not grep {mov E.X, E.X}
+
+%G = external global int
+
+int %test1(int %X, int %Y) {
+        %Z = add int %X, %Y
+        volatile store int %Y, int* %G
+        volatile store int %Z, int* %G
+        ret int %X
+}
+
+int %test2(int %X) {
+        %Z = add int %X, 1  ;; inc
+        volatile store int %Z, int* %G
+        ret int %X
+}
+
 //===---------------------------------------------------------------------===//
 
 We use push/pop of stack space around calls in situations where we don't have to.