From 5f36b46bf0fa9dbdb6caede9a6a1d65a640c4e1a Mon Sep 17 00:00:00 2001 From: Hal Finkel Date: Sun, 7 Sep 2014 21:37:59 +0000 Subject: [PATCH] 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. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217348 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/ScalarEvolution.cpp | 30 +++++-- .../ScalarEvolution/nsw-offset-assume.ll | 83 +++++++++++++++++++ 2 files changed, 107 insertions(+), 6 deletions(-) create mode 100644 test/Analysis/ScalarEvolution/nsw-offset-assume.ll diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index 00b485dedee..d1274d78a30 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -6313,13 +6313,22 @@ ScalarEvolution::isLoopBackedgeGuardedByCond(const Loop *L, BranchInst *LoopContinuePredicate = dyn_cast(Latch->getTerminator()); - if (!LoopContinuePredicate || - LoopContinuePredicate->isUnconditional()) - return false; + if (LoopContinuePredicate && LoopContinuePredicate->isConditional() && + isImpliedCond(Pred, LHS, RHS, + LoopContinuePredicate->getCondition(), + LoopContinuePredicate->getSuccessor(0) != L->getHeader())) + return true; + + // Check conditions due to any @llvm.assume intrinsics. + for (auto &CI : AT->assumptions(F)) { + if (!DT->dominates(CI, Latch->getTerminator())) + continue; + + if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false)) + return true; + } - return isImpliedCond(Pred, LHS, RHS, - LoopContinuePredicate->getCondition(), - LoopContinuePredicate->getSuccessor(0) != L->getHeader()); + return false; } /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected @@ -6353,6 +6362,15 @@ ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L, return true; } + // Check conditions due to any @llvm.assume intrinsics. + for (auto &CI : AT->assumptions(F)) { + if (!DT->dominates(CI, L->getHeader())) + continue; + + if (isImpliedCond(Pred, LHS, RHS, CI->getArgOperand(0), false)) + return true; + } + return false; } diff --git a/test/Analysis/ScalarEvolution/nsw-offset-assume.ll b/test/Analysis/ScalarEvolution/nsw-offset-assume.ll new file mode 100644 index 00000000000..29cf6585779 --- /dev/null +++ b/test/Analysis/ScalarEvolution/nsw-offset-assume.ll @@ -0,0 +1,83 @@ +; RUN: opt < %s -S -analyze -scalar-evolution | FileCheck %s + +; ScalarEvolution should be able to fold away the sign-extensions +; on this loop with a primary induction variable incremented with +; a nsw add of 2 (this test is derived from the nsw-offset.ll test, but uses an +; assume instead of a preheader conditional branch to guard the loop). + +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" + +define void @foo(i32 %no, double* nocapture %d, double* nocapture %q) nounwind { +entry: + %n = and i32 %no, 4294967294 + %0 = icmp sgt i32 %n, 0 ; [#uses=1] + tail call void @llvm.assume(i1 %0) + br label %bb.nph + +bb.nph: ; preds = %entry + br label %bb + +bb: ; preds = %bb.nph, %bb1 + %i.01 = phi i32 [ %16, %bb1 ], [ 0, %bb.nph ] ; [#uses=5] + +; CHECK: %1 = sext i32 %i.01 to i64 +; CHECK: --> {0,+,2}<%bb> + %1 = sext i32 %i.01 to i64 ; [#uses=1] + +; CHECK: %2 = getelementptr inbounds double* %d, i64 %1 +; CHECK: --> {%d,+,16}<%bb> + %2 = getelementptr inbounds double* %d, i64 %1 ; [#uses=1] + + %3 = load double* %2, align 8 ; [#uses=1] + %4 = sext i32 %i.01 to i64 ; [#uses=1] + %5 = getelementptr inbounds double* %q, i64 %4 ; [#uses=1] + %6 = load double* %5, align 8 ; [#uses=1] + %7 = or i32 %i.01, 1 ; [#uses=1] + +; CHECK: %8 = sext i32 %7 to i64 +; CHECK: --> {1,+,2}<%bb> + %8 = sext i32 %7 to i64 ; [#uses=1] + +; CHECK: %9 = getelementptr inbounds double* %q, i64 %8 +; CHECK: {(8 + %q),+,16}<%bb> + %9 = getelementptr inbounds double* %q, i64 %8 ; [#uses=1] + +; Artificially repeat the above three instructions, this time using +; add nsw instead of or. + %t7 = add nsw i32 %i.01, 1 ; [#uses=1] + +; CHECK: %t8 = sext i32 %t7 to i64 +; CHECK: --> {1,+,2}<%bb> + %t8 = sext i32 %t7 to i64 ; [#uses=1] + +; CHECK: %t9 = getelementptr inbounds double* %q, i64 %t8 +; CHECK: {(8 + %q),+,16}<%bb> + %t9 = getelementptr inbounds double* %q, i64 %t8 ; [#uses=1] + + %10 = load double* %9, align 8 ; [#uses=1] + %11 = fadd double %6, %10 ; [#uses=1] + %12 = fadd double %11, 3.200000e+00 ; [#uses=1] + %13 = fmul double %3, %12 ; [#uses=1] + %14 = sext i32 %i.01 to i64 ; [#uses=1] + %15 = getelementptr inbounds double* %d, i64 %14 ; [#uses=1] + store double %13, double* %15, align 8 + %16 = add nsw i32 %i.01, 2 ; [#uses=2] + br label %bb1 + +bb1: ; preds = %bb + %17 = icmp slt i32 %16, %n ; [#uses=1] + br i1 %17, label %bb, label %bb1.return_crit_edge + +bb1.return_crit_edge: ; preds = %bb1 + br label %return + +return: ; preds = %bb1.return_crit_edge, %entry + ret void +} + +declare void @llvm.assume(i1) nounwind + +; Note: Without the preheader assume, there is an 'smax' in the +; backedge-taken count expression: +; CHECK: Loop %bb: backedge-taken count is ((-1 + (2 * (%no /u 2))) /u 2) +; CHECK: Loop %bb: max backedge-taken count is 1073741822 -- 2.34.1