[llvm] 9dfea03 - [SCCP] Handle assume predicates

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2020-07-07T20:22:52+02:00
New Revision: 9dfea0351797e1e10b6e28e290c134c179eba504

URL: https://github.com/llvm/llvm-project/commit/9dfea0351797e1e10b6e28e290c134c179eba504
DIFF: https://github.com/llvm/llvm-project/commit/9dfea0351797e1e10b6e28e290c134c179eba504.diff

LOG: [SCCP] Handle assume predicates

Take assume predicates into account when visiting ssa.copy. The
handling is the same as for branch predicates, with the difference
that we're always on the true edge.

Differential Revision: https://reviews.llvm.org/D83257

Added: 
    llvm/test/Transforms/SCCP/assume.ll

Modified: 
    llvm/lib/Transforms/Scalar/SCCP.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/SCCP.cpp b/llvm/lib/Transforms/Scalar/SCCP.cpp
index c08007f49a63..d28846d6e6de 100644
--- a/llvm/lib/Transforms/Scalar/SCCP.cpp
+++ b/llvm/lib/Transforms/Scalar/SCCP.cpp
@@ -1247,16 +1247,24 @@ void SCCPSolver::handleCallResult(CallBase &CB) {
         return;
 
       Value *CopyOf = CB.getOperand(0);
-      auto *PI = getPredicateInfoFor(&CB);
-      auto *PBranch = dyn_cast_or_null<PredicateBranch>(PI);
       ValueLatticeElement OriginalVal = getValueState(CopyOf);
-      if (!PI || !PBranch) {
+      auto *PI = getPredicateInfoFor(&CB);
+      assert(PI && "Missing predicate info for ssa.copy");
+
+      CmpInst *Cmp;
+      bool TrueEdge;
+      if (auto *PBranch = dyn_cast<PredicateBranch>(PI)) {
+        Cmp = dyn_cast<CmpInst>(PBranch->Condition);
+        TrueEdge = PBranch->TrueEdge;
+      } else if (auto *PAssume = dyn_cast<PredicateAssume>(PI)) {
+        Cmp = dyn_cast<CmpInst>(PAssume->Condition);
+        TrueEdge = true;
+      } else {
         mergeInValue(ValueState[&CB], &CB, OriginalVal);
         return;
       }
 
       // Everything below relies on the condition being a comparison.
-      auto *Cmp = dyn_cast<CmpInst>(PBranch->Condition);
       if (!Cmp) {
         mergeInValue(ValueState[&CB], &CB, OriginalVal);
         return;
@@ -1281,7 +1289,7 @@ void SCCPSolver::handleCallResult(CallBase &CB) {
         return;
       }
 
-      if (!PBranch->TrueEdge)
+      if (!TrueEdge)
         Pred = CmpInst::getInversePredicate(Pred);
 
       ValueLatticeElement CondVal = getValueState(CmpOp1);

diff  --git a/llvm/test/Transforms/SCCP/assume.ll b/llvm/test/Transforms/SCCP/assume.ll
new file mode 100644
index 000000000000..764c1737c287
--- /dev/null
+++ b/llvm/test/Transforms/SCCP/assume.ll
@@ -0,0 +1,48 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -ipsccp -S | FileCheck %s
+
+declare void @use(i1)
+declare void @llvm.assume(i1)
+
+define void @basic(i32 %v) {
+; CHECK-LABEL: @basic(
+; CHECK-NEXT:    [[A1:%.*]] = icmp ult i32 [[V:%.*]], 10
+; CHECK-NEXT:    call void @llvm.assume(i1 [[A1]])
+; CHECK-NEXT:    [[A2:%.*]] = icmp ugt i32 [[V]], 5
+; CHECK-NEXT:    call void @llvm.assume(i1 [[A2]])
+; CHECK-NEXT:    call void @use(i1 true)
+; CHECK-NEXT:    [[C2:%.*]] = icmp ult i32 [[V]], 9
+; CHECK-NEXT:    call void @use(i1 [[C2]])
+; CHECK-NEXT:    call void @use(i1 false)
+; CHECK-NEXT:    [[C4:%.*]] = icmp ugt i32 [[V]], 8
+; CHECK-NEXT:    call void @use(i1 [[C4]])
+; CHECK-NEXT:    call void @use(i1 true)
+; CHECK-NEXT:    [[C6:%.*]] = icmp ugt i32 [[V]], 6
+; CHECK-NEXT:    call void @use(i1 [[C6]])
+; CHECK-NEXT:    call void @use(i1 false)
+; CHECK-NEXT:    [[C8:%.*]] = icmp ult i32 [[V]], 7
+; CHECK-NEXT:    call void @use(i1 [[C8]])
+; CHECK-NEXT:    ret void
+;
+  %a1 = icmp ult i32 %v, 10
+  call void @llvm.assume(i1 %a1)
+  %a2 = icmp ugt i32 %v, 5
+  call void @llvm.assume(i1 %a2)
+  %c1 = icmp ult i32 %v, 10
+  call void @use(i1 %c1)
+  %c2 = icmp ult i32 %v, 9
+  call void @use(i1 %c2)
+  %c3 = icmp ugt i32 %v, 9
+  call void @use(i1 %c3)
+  %c4 = icmp ugt i32 %v, 8
+  call void @use(i1 %c4)
+  %c5 = icmp ugt i32 %v, 5
+  call void @use(i1 %c5)
+  %c6 = icmp ugt i32 %v, 6
+  call void @use(i1 %c6)
+  %c7 = icmp ult i32 %v, 6
+  call void @use(i1 %c7)
+  %c8 = icmp ult i32 %v, 7
+  call void @use(i1 %c8)
+  ret void
+}