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| author | Owen Anderson <resistor@mac.com> | 2010-09-21 18:41:19 +0000 |
|---|---|---|
| committer | Owen Anderson <resistor@mac.com> | 2010-09-21 18:41:19 +0000 |
| commit | c004eec71b49ae13ee4d9f859c61cdb9ed092b22 (patch) | |
| tree | 23a74efbf817f08bb796242ade0c68d03bf68c17 /test | |
| parent | 89bfef003ec71792d078d489566655006b89bc43 (diff) | |
| download | llvm-c004eec71b49ae13ee4d9f859c61cdb9ed092b22.tar.gz llvm-c004eec71b49ae13ee4d9f859c61cdb9ed092b22.tar.bz2 llvm-c004eec71b49ae13ee4d9f859c61cdb9ed092b22.tar.xz | |
When adding the carry bit to another value on X86, exploit the fact that the carry-materialization
(sbbl x, x) sets the registers to 0 or ~0. Combined with two's complement arithmetic, we can fold
the intermediate AND and the ADD into a single SUB.
This fixes <rdar://problem/8449754>.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114460 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'test')
| -rw-r--r-- | test/CodeGen/X86/add-of-carry.ll | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/test/CodeGen/X86/add-of-carry.ll b/test/CodeGen/X86/add-of-carry.ll new file mode 100644 index 0000000000..4c2257494d --- /dev/null +++ b/test/CodeGen/X86/add-of-carry.ll @@ -0,0 +1,14 @@ +; RUN: llc < %s -march=x86 | FileCheck %s +; <rdar://problem/8449754> + +define i32 @add32carry(i32 %sum, i32 %x) nounwind readnone ssp { +entry: +; CHECK: sbbl %ecx, %ecx +; CHECK-NOT: addl +; CHECK: subl %ecx, %eax + %add4 = add i32 %x, %sum + %cmp = icmp ult i32 %add4, %x + %inc = zext i1 %cmp to i32 + %z.0 = add i32 %add4, %inc + ret i32 %z.0 +} |