now that all the pieces are in place, teach instcombine's

simplifydemandedbits to simplify instructions with *multiple
uses* in contexts where it can get away with it.  This allows
it to simplify the code in multi-use-or.ll into a single 'add 
double'.

This change is particularly interesting because it will cover
up for some common codegen bugs with large integers created due
to the recent SROA patch.  When working on fixing those bugs,
this should be disabled.

llvm-svn: 63481

1 files changed, 24 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/multi-use-or.ll b/llvm/test/Transforms/InstCombine/multi-use-or.ll
new file mode 100644
index 00000000000..85a8b34e2f6
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/multi-use-or.ll
@@ -0,0 +1,24 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {add double .sx, .sy}
+; The 'or' has multiple uses, make sure that this doesn't prevent instcombine
+; from propagating the extends to the truncs.
+
+define double @ScaleObjectAdd(double %sx, double %sy, double %sz) nounwind {
+entry:
+        %sx34 = bitcast double %sx to i64               ; <i64> [#uses=1]
+        %sx3435 = zext i64 %sx34 to i192                ; <i192> [#uses=1]
+        %sy22 = bitcast double %sy to i64               ; <i64> [#uses=1]
+        %sy2223 = zext i64 %sy22 to i192                ; <i192> [#uses=1]
+        %sy222324 = shl i192 %sy2223, 128               ; <i192> [#uses=1]
+        %sy222324.ins = or i192 %sx3435, %sy222324              ; <i192> [#uses=1]
+        
+        
+        %a = trunc i192 %sy222324.ins to i64            ; <i64> [#uses=1]
+        %b = bitcast i64 %a to double           ; <double> [#uses=1]
+        %c = lshr i192 %sy222324.ins, 128               ; <i192> [#uses=1]
+        %d = trunc i192 %c to i64               ; <i64> [#uses=1]
+        %e = bitcast i64 %d to double           ; <double> [#uses=1]
+        %f = add double %b, %e
+
+;        ret double %e
+        ret double %f
+}