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| author | Chris Lattner <sabre@nondot.org> | 2008-02-28 04:52:59 +0000 |
|---|---|---|
| committer | Chris Lattner <sabre@nondot.org> | 2008-02-28 04:52:59 +0000 |
| commit | 44a98ac8837a425418444b9ca02f009127b360be (patch) | |
| tree | 1b4c293fd954f85a6f0f84bb8e10ffb7a92b9f03 /lib/Target | |
| parent | 45c1edb4f781571f11fefb07a46a2c0f08523650 (diff) | |
| download | external_llvm-44a98ac8837a425418444b9ca02f009127b360be.zip external_llvm-44a98ac8837a425418444b9ca02f009127b360be.tar.gz external_llvm-44a98ac8837a425418444b9ca02f009127b360be.tar.bz2 | |
Add a random not very important note
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47704 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Target')
| -rw-r--r-- | lib/Target/X86/README.txt | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt index eda9314..fccddc7 100644 --- a/lib/Target/X86/README.txt +++ b/lib/Target/X86/README.txt @@ -1687,3 +1687,41 @@ doload64: ret //===---------------------------------------------------------------------===// + +We compile this function: + +define i32 @foo(i32 %a, i32 %b, i32 %c, i8 zeroext %d) nounwind { +entry: + %tmp2 = icmp eq i8 %d, 0 ; <i1> [#uses=1] + br i1 %tmp2, label %bb7, label %bb + +bb: ; preds = %entry + %tmp6 = add i32 %b, %a ; <i32> [#uses=1] + ret i32 %tmp6 + +bb7: ; preds = %entry + %tmp10 = sub i32 %a, %c ; <i32> [#uses=1] + ret i32 %tmp10 +} + +to: + +_foo: + cmpb $0, 16(%esp) + movl 12(%esp), %ecx + movl 8(%esp), %eax + movl 4(%esp), %edx + je LBB1_2 # bb7 +LBB1_1: # bb + addl %edx, %eax + ret +LBB1_2: # bb7 + movl %edx, %eax + subl %ecx, %eax + ret + +The coallescer could coallesce "edx" with "eax" to avoid the movl in LBB1_2 +if it commuted the addl in LBB1_1. + +//===---------------------------------------------------------------------===// + |