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Make use @llvm.assume for loop guards in ScalarEvolution
This adds a basic (but important) use of @llvm.assume calls in ScalarEvolution. When SE is attempting to validate a condition guarding a loop (such as whether or not the loop count can be zero), this check should also include dominating assumptions. llvm-svn: 217348
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@ -6313,13 +6313,22 @@ ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L,
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BranchInst *LoopContinuePredicate =
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BranchInst *LoopContinuePredicate =
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dyn_cast<BranchInst>(Latch->getTerminator());
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dyn_cast<BranchInst>(Latch->getTerminator());
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if (!LoopContinuePredicate ||
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if (LoopContinuePredicate && LoopContinuePredicate->isConditional() &&
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LoopContinuePredicate->isUnconditional())
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isImpliedCond(Pred, LHS, RHS,
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return false;
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LoopContinuePredicate->getCondition(),
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LoopContinuePredicate->getSuccessor(0) != L->getHeader()))
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return true;
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return isImpliedCond(Pred, LHS, RHS,
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// Check conditions due to any @llvm.assume intrinsics.
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LoopContinuePredicate->getCondition(),
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for (auto &CI : AT->assumptions(F)) {
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LoopContinuePredicate->getSuccessor(0) != L->getHeader());
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if (!DT->dominates(CI, Latch->getTerminator()))
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continue;
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if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
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return true;
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}
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return false;
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}
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}
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/// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
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/// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
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@ -6353,6 +6362,15 @@ ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
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return true;
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return true;
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}
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}
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// Check conditions due to any @llvm.assume intrinsics.
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for (auto &CI : AT->assumptions(F)) {
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if (!DT->dominates(CI, L->getHeader()))
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continue;
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if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false))
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return true;
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}
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return false;
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return false;
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}
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}
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83
test/Analysis/ScalarEvolution/nsw-offset-assume.ll
Normal file
83
test/Analysis/ScalarEvolution/nsw-offset-assume.ll
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@ -0,0 +1,83 @@
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; RUN: opt < %s -S -analyze -scalar-evolution | FileCheck %s
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; ScalarEvolution should be able to fold away the sign-extensions
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; on this loop with a primary induction variable incremented with
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; a nsw add of 2 (this test is derived from the nsw-offset.ll test, but uses an
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; assume instead of a preheader conditional branch to guard the loop).
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target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
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define void @foo(i32 %no, double* nocapture %d, double* nocapture %q) nounwind {
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entry:
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%n = and i32 %no, 4294967294
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%0 = icmp sgt i32 %n, 0 ; <i1> [#uses=1]
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tail call void @llvm.assume(i1 %0)
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br label %bb.nph
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bb.nph: ; preds = %entry
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br label %bb
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bb: ; preds = %bb.nph, %bb1
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%i.01 = phi i32 [ %16, %bb1 ], [ 0, %bb.nph ] ; <i32> [#uses=5]
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; CHECK: %1 = sext i32 %i.01 to i64
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; CHECK: --> {0,+,2}<nuw><nsw><%bb>
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%1 = sext i32 %i.01 to i64 ; <i64> [#uses=1]
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; CHECK: %2 = getelementptr inbounds double* %d, i64 %1
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; CHECK: --> {%d,+,16}<nsw><%bb>
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%2 = getelementptr inbounds double* %d, i64 %1 ; <double*> [#uses=1]
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%3 = load double* %2, align 8 ; <double> [#uses=1]
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%4 = sext i32 %i.01 to i64 ; <i64> [#uses=1]
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%5 = getelementptr inbounds double* %q, i64 %4 ; <double*> [#uses=1]
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%6 = load double* %5, align 8 ; <double> [#uses=1]
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%7 = or i32 %i.01, 1 ; <i32> [#uses=1]
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; CHECK: %8 = sext i32 %7 to i64
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; CHECK: --> {1,+,2}<nuw><nsw><%bb>
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%8 = sext i32 %7 to i64 ; <i64> [#uses=1]
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; CHECK: %9 = getelementptr inbounds double* %q, i64 %8
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; CHECK: {(8 + %q),+,16}<nsw><%bb>
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%9 = getelementptr inbounds double* %q, i64 %8 ; <double*> [#uses=1]
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; Artificially repeat the above three instructions, this time using
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; add nsw instead of or.
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%t7 = add nsw i32 %i.01, 1 ; <i32> [#uses=1]
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; CHECK: %t8 = sext i32 %t7 to i64
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; CHECK: --> {1,+,2}<nuw><nsw><%bb>
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%t8 = sext i32 %t7 to i64 ; <i64> [#uses=1]
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; CHECK: %t9 = getelementptr inbounds double* %q, i64 %t8
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; CHECK: {(8 + %q),+,16}<nsw><%bb>
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%t9 = getelementptr inbounds double* %q, i64 %t8 ; <double*> [#uses=1]
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%10 = load double* %9, align 8 ; <double> [#uses=1]
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%11 = fadd double %6, %10 ; <double> [#uses=1]
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%12 = fadd double %11, 3.200000e+00 ; <double> [#uses=1]
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%13 = fmul double %3, %12 ; <double> [#uses=1]
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%14 = sext i32 %i.01 to i64 ; <i64> [#uses=1]
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%15 = getelementptr inbounds double* %d, i64 %14 ; <double*> [#uses=1]
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store double %13, double* %15, align 8
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%16 = add nsw i32 %i.01, 2 ; <i32> [#uses=2]
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br label %bb1
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bb1: ; preds = %bb
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%17 = icmp slt i32 %16, %n ; <i1> [#uses=1]
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br i1 %17, label %bb, label %bb1.return_crit_edge
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bb1.return_crit_edge: ; preds = %bb1
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br label %return
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return: ; preds = %bb1.return_crit_edge, %entry
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ret void
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}
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declare void @llvm.assume(i1) nounwind
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; Note: Without the preheader assume, there is an 'smax' in the
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; backedge-taken count expression:
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; CHECK: Loop %bb: backedge-taken count is ((-1 + (2 * (%no /u 2))) /u 2)
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; CHECK: Loop %bb: max backedge-taken count is 1073741822
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