Make the 'icmp pred trunc(ext(X)), CST --> icmp pred X, ext(trunc(CST))'

transformation much more careful. Truncating binary '01' to '1' sounds like it's
safe until you realize that it switched from positive to negative under a signed
interpretation, and that depends on the icmp predicate.

Also a few miscellaneous cleanups.

llvm-svn: 97721

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/2010-03-03-ExtElim.ll b/llvm/test/Transforms/InstCombine/2010-03-03-ExtElim.ll
new file mode 100644
index 00000000000..2df12d670ad
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/2010-03-03-ExtElim.ll
@@ -0,0 +1,18 @@
+; RUN: opt -instcombine -S %s | FileCheck %s
+; PR6486
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
+target triple = "i386-unknown-linux-gnu"
+
+@g_92 = common global [2 x i32*] zeroinitializer, align 4 ; <[2 x i32*]*> [#uses=1]
+@g_177 = constant i32** bitcast (i8* getelementptr (i8* bitcast ([2 x i32*]* @g_92 to i8*), i64 4) to i32**), align 4 ; <i32***> [#uses=1]
+
+define i1 @test() nounwind {
+; CHECK: @test
+  %tmp = load i32*** @g_177                       ; <i32**> [#uses=1]
+  %cmp = icmp ne i32** null, %tmp                 ; <i1> [#uses=1]
+  %conv = zext i1 %cmp to i32                     ; <i32> [#uses=1]
+  %cmp1 = icmp sle i32 0, %conv                   ; <i1> [#uses=1]
+  ret i1 %cmp1
+; CHECK: ret i1 true
+}