[llvm] 8453fbf - [ValueTracking] Compute known bits of min/max intrinsics

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2020-09-08T21:08:17+02:00
New Revision: 8453fbf0889e22cf9bbb74c65e36cf8abbcec7b4

URL: https://github.com/llvm/llvm-project/commit/8453fbf0889e22cf9bbb74c65e36cf8abbcec7b4
DIFF: https://github.com/llvm/llvm-project/commit/8453fbf0889e22cf9bbb74c65e36cf8abbcec7b4.diff

LOG: [ValueTracking] Compute known bits of min/max intrinsics

Implement known bits for the min/max intrinsics based on the
recently added KnownBits primitives.

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp
    llvm/test/Transforms/InstCombine/minmax-intrinsics.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 6e5a7195bb19..5eb66e96e1d8 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1739,6 +1739,26 @@ static void computeKnownBitsFromOperator(const Operator *I,
         }
         break;
       }
+      case Intrinsic::umin:
+        computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
+        computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
+        Known = KnownBits::umin(Known, Known2);
+        break;
+      case Intrinsic::umax:
+        computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
+        computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
+        Known = KnownBits::umax(Known, Known2);
+        break;
+      case Intrinsic::smin:
+        computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
+        computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
+        Known = KnownBits::smin(Known, Known2);
+        break;
+      case Intrinsic::smax:
+        computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
+        computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
+        Known = KnownBits::smax(Known, Known2);
+        break;
       case Intrinsic::x86_sse42_crc32_64_64:
         Known.Zero.setBitsFrom(32);
         break;

diff  --git a/llvm/test/Transforms/InstCombine/minmax-intrinsics.ll b/llvm/test/Transforms/InstCombine/minmax-intrinsics.ll
index d808d5fc4244..797f85d94447 100644
--- a/llvm/test/Transforms/InstCombine/minmax-intrinsics.ll
+++ b/llvm/test/Transforms/InstCombine/minmax-intrinsics.ll
@@ -8,10 +8,7 @@ declare i8 @llvm.smax.i8(i8, i8)
 
 define i8 @umin_known_bits(i8 %x, i8 %y) {
 ; CHECK-LABEL: @umin_known_bits(
-; CHECK-NEXT:    [[X2:%.*]] = and i8 [[X:%.*]], 127
-; CHECK-NEXT:    [[M:%.*]] = call i8 @llvm.umin.i8(i8 [[X2]], i8 [[Y:%.*]])
-; CHECK-NEXT:    [[R:%.*]] = and i8 [[M]], -128
-; CHECK-NEXT:    ret i8 [[R]]
+; CHECK-NEXT:    ret i8 0
 ;
   %x2 = and i8 %x, 127
   %m = call i8 @llvm.umin.i8(i8 %x2, i8 %y)
@@ -21,10 +18,7 @@ define i8 @umin_known_bits(i8 %x, i8 %y) {
 
 define i8 @umax_known_bits(i8 %x, i8 %y) {
 ; CHECK-LABEL: @umax_known_bits(
-; CHECK-NEXT:    [[X2:%.*]] = or i8 [[X:%.*]], -128
-; CHECK-NEXT:    [[M:%.*]] = call i8 @llvm.umax.i8(i8 [[X2]], i8 [[Y:%.*]])
-; CHECK-NEXT:    [[R:%.*]] = and i8 [[M]], -128
-; CHECK-NEXT:    ret i8 [[R]]
+; CHECK-NEXT:    ret i8 -128
 ;
   %x2 = or i8 %x, -128
   %m = call i8 @llvm.umax.i8(i8 %x2, i8 %y)
@@ -34,10 +28,7 @@ define i8 @umax_known_bits(i8 %x, i8 %y) {
 
 define i8 @smin_known_bits(i8 %x, i8 %y) {
 ; CHECK-LABEL: @smin_known_bits(
-; CHECK-NEXT:    [[X2:%.*]] = or i8 [[X:%.*]], -128
-; CHECK-NEXT:    [[M:%.*]] = call i8 @llvm.smin.i8(i8 [[X2]], i8 [[Y:%.*]])
-; CHECK-NEXT:    [[R:%.*]] = and i8 [[M]], -128
-; CHECK-NEXT:    ret i8 [[R]]
+; CHECK-NEXT:    ret i8 -128
 ;
   %x2 = or i8 %x, -128
   %m = call i8 @llvm.smin.i8(i8 %x2, i8 %y)
@@ -47,10 +38,7 @@ define i8 @smin_known_bits(i8 %x, i8 %y) {
 
 define i8 @smax_known_bits(i8 %x, i8 %y) {
 ; CHECK-LABEL: @smax_known_bits(
-; CHECK-NEXT:    [[X2:%.*]] = and i8 [[X:%.*]], 127
-; CHECK-NEXT:    [[M:%.*]] = call i8 @llvm.smax.i8(i8 [[X2]], i8 [[Y:%.*]])
-; CHECK-NEXT:    [[R:%.*]] = and i8 [[M]], -128
-; CHECK-NEXT:    ret i8 [[R]]
+; CHECK-NEXT:    ret i8 0
 ;
   %x2 = and i8 %x, 127
   %m = call i8 @llvm.smax.i8(i8 %x2, i8 %y)