[PATCH] D87183: [SCCP] Compute ranges for supported intrinsics

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
nikic added reviewers: fhahn, efriedma.
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For intrinsics supported by ConstantRange, compute the result range based on the argument ranges. We do this independently of whether some or all of the input ranges are full, as we can often still constrain the result in some way.


https://reviews.llvm.org/D87183

Files:
  llvm/lib/Transforms/Scalar/SCCP.cpp
  llvm/test/Transforms/SCCP/intrinsics.ll


Index: llvm/test/Transforms/SCCP/intrinsics.ll
===================================================================
--- llvm/test/Transforms/SCCP/intrinsics.ll
+++ llvm/test/Transforms/SCCP/intrinsics.ll
@@ -12,10 +12,8 @@
 ; CHECK-LABEL: @abs1(
 ; CHECK-NEXT:    [[X:%.*]] = load i8, i8* [[P:%.*]], align 1, [[RNG0:!range !.*]]
 ; CHECK-NEXT:    [[ABS:%.*]] = call i8 @llvm.abs.i8(i8 [[X]], i1 false)
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp sge i8 [[ABS]], 0
-; CHECK-NEXT:    call void @use(i1 [[CMP1]])
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp slt i8 [[ABS]], 10
-; CHECK-NEXT:    call void @use(i1 [[CMP2]])
+; CHECK-NEXT:    call void @use(i1 true)
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[CMP3:%.*]] = icmp sge i8 [[ABS]], 1
 ; CHECK-NEXT:    call void @use(i1 [[CMP3]])
 ; CHECK-NEXT:    [[CMP4:%.*]] = icmp slt i8 [[ABS]], 9
@@ -40,8 +38,7 @@
 define void @abs2(i8 %x) {
 ; CHECK-LABEL: @abs2(
 ; CHECK-NEXT:    [[ABS:%.*]] = call i8 @llvm.abs.i8(i8 [[X:%.*]], i1 true)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i8 [[ABS]], 0
-; CHECK-NEXT:    call void @use(i1 [[CMP]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    ret void
 ;
   %abs = call i8 @llvm.abs.i8(i8 %x, i1 true)
@@ -68,10 +65,8 @@
 ; CHECK-NEXT:    [[X1:%.*]] = load i8, i8* [[P1:%.*]], align 1, [[RNG1:!range !.*]]
 ; CHECK-NEXT:    [[X2:%.*]] = load i8, i8* [[P2:%.*]], align 1, [[RNG2:!range !.*]]
 ; CHECK-NEXT:    [[M:%.*]] = call i8 @llvm.umax.i8(i8 [[X1]], i8 [[X2]])
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp uge i8 [[M]], 5
-; CHECK-NEXT:    call void @use(i1 [[CMP1]])
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp ult i8 [[M]], 15
-; CHECK-NEXT:    call void @use(i1 [[CMP2]])
+; CHECK-NEXT:    call void @use(i1 true)
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    [[CMP3:%.*]] = icmp uge i8 [[M]], 6
 ; CHECK-NEXT:    call void @use(i1 [[CMP3]])
 ; CHECK-NEXT:    [[CMP4:%.*]] = icmp ult i8 [[M]], 14
@@ -95,8 +90,7 @@
 define void @umax2(i8 %x) {
 ; CHECK-LABEL: @umax2(
 ; CHECK-NEXT:    [[M:%.*]] = call i8 @llvm.umax.i8(i8 [[X:%.*]], i8 10)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp uge i8 [[M]], 10
-; CHECK-NEXT:    call void @use(i1 [[CMP]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    ret void
 ;
   %m = call i8 @llvm.umax.i8(i8 %x, i8 10)
Index: llvm/lib/Transforms/Scalar/SCCP.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/SCCP.cpp
+++ llvm/lib/Transforms/Scalar/SCCP.cpp
@@ -1350,6 +1350,25 @@
 
       return (void)mergeInValue(IV, &CB, CopyOfVal);
     }
+
+    if (ConstantRange::isIntrinsicSupported(II->getIntrinsicID())) {
+      // Compute result range for intrinsics supported by ConstantRange.
+      // Do this even if we don't know a range for all operands, as we may
+      // still know something about the result range, e.g. of abs(x).
+      SmallVector<ConstantRange, 2> OpRanges;
+      for (Value *Op : II->args()) {
+        const ValueLatticeElement &State = getValueState(Op);
+        if (State.isConstantRange())
+          OpRanges.push_back(State.getConstantRange());
+        else
+          OpRanges.push_back(
+              ConstantRange::getFull(Op->getType()->getScalarSizeInBits()));
+      }
+
+      ConstantRange Result =
+          ConstantRange::intrinsic(II->getIntrinsicID(), OpRanges);
+      return (void)mergeInValue(II, ValueLatticeElement::getRange(Result));
+    }
   }
 
   // The common case is that we aren't tracking the callee, either because we


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