[InstCombine] add tests to show missed canonicalization of min/max; NFC

Unfortunately, recognizing these in value tracking may cause us to hit
a hack in InstCombiner::visitICmpInst() more often:
http://lists.llvm.org/pipermail/llvm-dev/2017-January/109340.html

...but besides being the obviously Right Thing To Do, there's a clear
codegen win from identifying these patterns for several targets.

llvm-svn: 292655

diff --git a/llvm/test/Transforms/InstCombine/minmax-fold.ll b/llvm/test/Transforms/InstCombine/minmax-fold.ll
index e39f7f4..ec838e2 100644 (file)
--- a/llvm/test/Transforms/InstCombine/minmax-fold.ll
+++ b/llvm/test/Transforms/InstCombine/minmax-fold.ll
@@ -339,3 +339,74 @@ define i32 @test75(i32 %x) {
   ret i32 %retval
 }
 
+; The next 4 tests are value clamping with constants:
+; https://llvm.org/bugs/show_bug.cgi?id=31693
+
+; (X <s C1) ? C1 : SMIN(X, C2) ==> SMAX(SMIN(X, C2), C1)
+
+define i32 @clamp_signed1(i32 %x) {
+; CHECK-LABEL: @clamp_signed1(
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp slt i32 %x, 255
+; CHECK-NEXT:    [[MIN:%.*]] = select i1 [[CMP2]], i32 %x, i32 255
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 %x, 15
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[CMP1]], i32 15, i32 [[MIN]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %cmp2 = icmp slt i32 %x, 255
+  %min = select i1 %cmp2, i32 %x, i32 255
+  %cmp1 = icmp slt i32 %x, 15
+  %r = select i1 %cmp1, i32 15, i32 %min
+  ret i32 %r
+}
+
+; (X >s C1) ? C1 : SMAX(X, C2) ==> SMIN(SMAX(X, C2), C1)
+
+define i32 @clamp_signed2(i32 %x) {
+; CHECK-LABEL: @clamp_signed2(
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp sgt i32 %x, 15
+; CHECK-NEXT:    [[MAX:%.*]] = select i1 [[CMP2]], i32 %x, i32 15
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp sgt i32 %x, 255
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[CMP1]], i32 255, i32 [[MAX]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %cmp2 = icmp sgt i32 %x, 15
+  %max = select i1 %cmp2, i32 %x, i32 15
+  %cmp1 = icmp sgt i32 %x, 255
+  %r = select i1 %cmp1, i32 255, i32 %max
+  ret i32 %r
+}
+
+; (X <u C1) ? C1 : UMIN(X, C2) ==> UMAX(UMIN(X, C2), C1)
+
+define i32 @clamp_unsigned1(i32 %x) {
+; CHECK-LABEL: @clamp_unsigned1(
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp ult i32 %x, 255
+; CHECK-NEXT:    [[MIN:%.*]] = select i1 [[CMP2]], i32 %x, i32 255
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp ult i32 %x, 15
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[CMP1]], i32 15, i32 [[MIN]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %cmp2 = icmp ult i32 %x, 255
+  %min = select i1 %cmp2, i32 %x, i32 255
+  %cmp1 = icmp ult i32 %x, 15
+  %r = select i1 %cmp1, i32 15, i32 %min
+  ret i32 %r
+}
+
+; (X >u C1) ? C1 : UMAX(X, C2) ==> UMIN(UMAX(X, C2), C1)
+
+define i32 @clamp_unsigned2(i32 %x) {
+; CHECK-LABEL: @clamp_unsigned2(
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp ugt i32 %x, 15
+; CHECK-NEXT:    [[MAX:%.*]] = select i1 [[CMP2]], i32 %x, i32 15
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp ugt i32 %x, 255
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[CMP1]], i32 255, i32 [[MAX]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %cmp2 = icmp ugt i32 %x, 15
+  %max = select i1 %cmp2, i32 %x, i32 15
+  %cmp1 = icmp ugt i32 %x, 255
+  %r = select i1 %cmp1, i32 255, i32 %max
+  ret i32 %r
+}
+