Changes in directory llvm/lib/Target/X86:
README.txt updated: 1.152 -> 1.153
---
Log message:
add a note
---
Diffs of the changes: (+52 -0)
README.txt | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 52 insertions(+)
Index: llvm/lib/Target/X86/README.txt
diff -u llvm/lib/Target/X86/README.txt:1.152
llvm/lib/Target/X86/README.txt:1.153
--- llvm/lib/Target/X86/README.txt:1.152 Mon Jan 15 00:25:39 2007
+++ llvm/lib/Target/X86/README.txt Sun Jan 21 01:03:37 2007
@@ -830,3 +830,55 @@
the pxor is not needed, we could compare the value against itself.
+//===---------------------------------------------------------------------===//
+
+These two functions have identical effects:
+
+unsigned int f(unsigned int i, unsigned int n) {++i; if (i == n) ++i; return
i;}
+unsigned int f2(unsigned int i, unsigned int n) {++i; i += i == n; return i;}
+
+We currently compile them to:
+
+_f:
+ movl 4(%esp), %eax
+ movl %eax, %ecx
+ incl %ecx
+ movl 8(%esp), %edx
+ cmpl %edx, %ecx
+ jne LBB1_2 #UnifiedReturnBlock
+LBB1_1: #cond_true
+ addl $2, %eax
+ ret
+LBB1_2: #UnifiedReturnBlock
+ movl %ecx, %eax
+ ret
+_f2:
+ movl 4(%esp), %eax
+ movl %eax, %ecx
+ incl %ecx
+ cmpl 8(%esp), %ecx
+ sete %cl
+ movzbl %cl, %ecx
+ leal 1(%ecx,%eax), %eax
+ ret
+
+both of which are inferior to GCC's:
+
+_f:
+ movl 4(%esp), %edx
+ leal 1(%edx), %eax
+ addl $2, %edx
+ cmpl 8(%esp), %eax
+ cmove %edx, %eax
+ ret
+_f2:
+ movl 4(%esp), %eax
+ addl $1, %eax
+ xorl %edx, %edx
+ cmpl 8(%esp), %eax
+ sete %dl
+ addl %edx, %eax
+ ret
+
+//===---------------------------------------------------------------------===//
+
_______________________________________________
llvm-commits mailing list
llvm-commits@cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
