[InstCombine] Add range metadata to cttz/ctlz/ctpop intrinsic calls based on known bits

Summary:
I noticed that passing known bits across these intrinsics isn't great at capturing the information we really know. Turning known bits of the input into known bits of a count output isn't able to convey a lot of what we really know.

This patch adds range metadata to these intrinsics based on the known bits.

Currently the patch punts if we already have range metadata present.

Reviewers: spatel, RKSimon, davide, majnemer

Reviewed By: RKSimon

Subscribers: sanjoy, hfinkel, llvm-commits

Differential Revision: https://reviews.llvm.org/D32582

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@305927 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 29 insertions, 12 deletions

diff --git a/test/Transforms/InstCombine/intrinsics.ll b/test/Transforms/InstCombine/intrinsics.ll
index 1b1ed606868..c294d79f15e 100644
--- a/test/Transforms/InstCombine/intrinsics.ll
+++ b/test/Transforms/InstCombine/intrinsics.ll
@@ -16,6 +16,8 @@ declare %ov.result.32 @llvm.umul.with.overflow.i32(i32, i32) nounwind readnone
 declare double @llvm.powi.f64(double, i32) nounwind readonly
 declare i32 @llvm.cttz.i32(i32, i1) nounwind readnone
 declare i32 @llvm.ctlz.i32(i32, i1) nounwind readnone
+declare i1 @llvm.cttz.i1(i1, i1) nounwind readnone
+declare i1 @llvm.ctlz.i1(i1, i1) nounwind readnone
 declare i32 @llvm.ctpop.i32(i32) nounwind readnone
 declare <2 x i32> @llvm.cttz.v2i32(<2 x i32>, i1) nounwind readnone
 declare <2 x i32> @llvm.ctlz.v2i32(<2 x i32>, i1) nounwind readnone
@@ -293,6 +295,16 @@ define <2 x i32> @cttz_vec(<2 x i32> %a) {
   ret <2 x i32> %count
 }
 
+; Make sure we don't add range metadata to i1 cttz.
+define i1 @cttz_i1(i1 %arg) {
+; CHECK-LABEL: @cttz_i1(
+; CHECK-NEXT:    [[CNT:%.*]] = call i1 @llvm.cttz.i1(i1 [[ARG:%.*]], i1 false) #2
+; CHECK-NEXT:    ret i1 [[CNT]]
+;
+  %cnt = call i1 @llvm.cttz.i1(i1 %arg, i1 false) nounwind readnone
+  ret i1 %cnt
+}
+
 define i1 @cttz_knownbits(i32 %arg) {
 ; CHECK-LABEL: @cttz_knownbits(
 ; CHECK-NEXT:    ret i1 false
@@ -316,7 +328,7 @@ define <2 x i1> @cttz_knownbits_vec(<2 x i32> %arg) {
 define i1 @cttz_knownbits2(i32 %arg) {
 ; CHECK-LABEL: @cttz_knownbits2(
 ; CHECK-NEXT:    [[OR:%.*]] = or i32 [[ARG:%.*]], 4
-; CHECK-NEXT:    [[CNT:%.*]] = call i32 @llvm.cttz.i32(i32 [[OR]], i1 true)
+; CHECK-NEXT:    [[CNT:%.*]] = call i32 @llvm.cttz.i32(i32 [[OR]], i1 true) #2, !range ![[CTTZ_RANGE:[0-9]+]]
 ; CHECK-NEXT:    [[RES:%.*]] = icmp eq i32 [[CNT]], 2
 ; CHECK-NEXT:    ret i1 [[RES]]
 ;
@@ -339,13 +351,9 @@ define <2 x i1> @cttz_knownbits2_vec(<2 x i32> %arg) {
   ret <2 x i1> %res
 }
 
-; TODO: The icmp is unnecessary given the known bits of the input.
 define i1 @cttz_knownbits3(i32 %arg) {
 ; CHECK-LABEL: @cttz_knownbits3(
-; CHECK-NEXT:    [[OR:%.*]] = or i32 [[ARG:%.*]], 4
-; CHECK-NEXT:    [[CNT:%.*]] = call i32 @llvm.cttz.i32(i32 [[OR]], i1 true) #2
-; CHECK-NEXT:    [[RES:%.*]] = icmp eq i32 [[CNT]], 3
-; CHECK-NEXT:    ret i1 [[RES]]
+; CHECK-NEXT:    ret i1 false
 ;
   %or = or i32 %arg, 4
   %cnt = call i32 @llvm.cttz.i32(i32 %or, i1 true) nounwind readnone
@@ -387,6 +395,16 @@ define <2 x i8> @ctlz_vec(<2 x i8> %a) {
   ret <2 x i8> %count
 }
 
+; Make sure we don't add range metadata to i1 ctlz.
+define i1 @ctlz_i1(i1 %arg) {
+; CHECK-LABEL: @ctlz_i1(
+; CHECK-NEXT:    [[CNT:%.*]] = call i1 @llvm.ctlz.i1(i1 [[ARG:%.*]], i1 false) #2
+; CHECK-NEXT:    ret i1 [[CNT]]
+;
+  %cnt = call i1 @llvm.ctlz.i1(i1 %arg, i1 false) nounwind readnone
+  ret i1 %cnt
+}
+
 define i1 @ctlz_knownbits(i8 %arg) {
 ; CHECK-LABEL: @ctlz_knownbits(
 ; CHECK-NEXT:    ret i1 false
@@ -410,7 +428,7 @@ define <2 x i1> @ctlz_knownbits_vec(<2 x i8> %arg) {
 define i1 @ctlz_knownbits2(i8 %arg) {
 ; CHECK-LABEL: @ctlz_knownbits2(
 ; CHECK-NEXT:    [[OR:%.*]] = or i8 [[ARG:%.*]], 32
-; CHECK-NEXT:    [[CNT:%.*]] = call i8 @llvm.ctlz.i8(i8 [[OR]], i1 true)
+; CHECK-NEXT:    [[CNT:%.*]] = call i8 @llvm.ctlz.i8(i8 [[OR]], i1 true) #2, !range ![[CTLZ_RANGE:[0-9]+]]
 ; CHECK-NEXT:    [[RES:%.*]] = icmp eq i8 [[CNT]], 2
 ; CHECK-NEXT:    ret i1 [[RES]]
 ;
@@ -433,13 +451,9 @@ define <2 x i1> @ctlz_knownbits2_vec(<2 x i8> %arg) {
   ret <2 x i1> %res
 }
 
-; TODO: The icmp is unnecessary given the known bits of the input.
 define i1 @ctlz_knownbits3(i8 %arg) {
 ; CHECK-LABEL: @ctlz_knownbits3(
-; CHECK-NEXT:    [[OR:%.*]] = or i8 [[ARG:%.*]], 32
-; CHECK-NEXT:    [[CNT:%.*]] = call i8 @llvm.ctlz.i8(i8 [[OR]], i1 true) #2
-; CHECK-NEXT:    [[RES:%.*]] = icmp eq i8 [[CNT]], 3
-; CHECK-NEXT:    ret i1 [[RES]]
+; CHECK-NEXT:    ret i1 false
 ;
   %or = or i8 %arg, 32
   %cnt = call i8 @llvm.ctlz.i8(i8 %or, i1 true) nounwind readnone
@@ -790,3 +804,6 @@ define void @nearbyint(double *%P) {
   store volatile double %C, double* %P
   ret void
 }
+
+; CHECK: [[CTTZ_RANGE]] = !{i32 0, i32 3}
+; CHECK: [[CTLZ_RANGE]] = !{i8 0, i8 3}