Fix the CBE's handling of instructions whose result is an i1. Previously,

we did not truncate the value down to i1 with (x&1).  This caused a problem
when the computation of x was nontrivial, for example, "add i1 1, 1" would 
return 2 instead of 0.

This makes the testcase compile into:

...
  llvm_cbe_t = (((llvm_cbe_r == 0u) + (llvm_cbe_r == 0u))&1);
  llvm_cbe_u = (((unsigned int )(bool )llvm_cbe_t));
...

instead of:

...
  llvm_cbe_t = ((llvm_cbe_r == 0u) + (llvm_cbe_r == 0u));
  llvm_cbe_u = (((unsigned int )(bool )llvm_cbe_t));
...

This fixes a miscompilation of mediabench/adpcm/rawdaudio/rawdaudio and
403.gcc with the CBE, regressions from LLVM 2.2. Tanya, please pull 
this into the release branch.

llvm-svn: 51813

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/CBackend/2008-05-31-BoolOverflow.ll b/llvm/test/CodeGen/CBackend/2008-05-31-BoolOverflow.ll
new file mode 100644
index 00000000000..52e02590078
--- /dev/null
+++ b/llvm/test/CodeGen/CBackend/2008-05-31-BoolOverflow.ll
@@ -0,0 +1,14 @@
+; RUN: llvm-as < %s | llc -march=c | grep {llvm_cbe_t.*&1}
+define i32 @test(i32 %r) {
+  %s = icmp eq i32 %r, 0
+  %t = add i1 %s, %s
+  %u = zext i1 %t to i32
+  br i1 %t, label %A, label %B
+A:
+
+  ret i32 %u
+B:
+
+  %v = select i1 %t, i32 %r, i32 %u
+  ret i32 %v
+}