From: Artur Pilipenko <apilipenko@azulsystems.com>
Date: Mon, 27 Feb 2017 15:44:49 +0000 (+0000)
Subject: Loop predication expand both sides of the widened condition
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=7e587ddfd9602c06fec1a6762eea028b83d97541;p=llvm

Loop predication expand both sides of the widened condition

This is a fix for a loop predication bug which resulted in malformed IR generation.

Loop invariant side of the widened condition is not guaranteed to be available in the preheader as is, so we need to expand it as well. See added unsigned_loop_0_to_n_hoist_length test for example.

Reviewed By: sanjoy, mkazantsev

Differential Revision: https://reviews.llvm.org/D30099


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296345 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Scalar/LoopPredication.cpp b/lib/Transforms/Scalar/LoopPredication.cpp
index fac2b8aecc8..0ce60442932 100644
--- a/lib/Transforms/Scalar/LoopPredication.cpp
+++ b/lib/Transforms/Scalar/LoopPredication.cpp
@@ -141,10 +141,9 @@ Optional<Value *> LoopPredication::widenICmpRangeCheck(ICmpInst *ICI,
     std::swap(LHSS, RHSS);
     Pred = ICmpInst::getSwappedPredicate(Pred);
   }
-  if (!SE->isLoopInvariant(RHSS, L))
+  if (!SE->isLoopInvariant(RHSS, L) || !isSafeToExpand(RHSS, *SE))
     return None;
 
-  Value *Bound = RHS;
   const SCEVAddRecExpr *IndexAR = dyn_cast<SCEVAddRecExpr>(LHSS);
   if (!IndexAR || IndexAR->getLoop() != L)
     return None;
@@ -176,9 +175,12 @@ Optional<Value *> LoopPredication::widenICmpRangeCheck(ICmpInst *ICI,
 
   DEBUG(dbgs() << "NewLHSS is loop invariant and safe to expand. Expand!\n");
 
-  Value *NewLHS = Expander.expandCodeFor(NewLHSS, Bound->getType(),
-                                         Preheader->getTerminator());
-  return Builder.CreateICmp(Pred, NewLHS, Bound);
+  Type *Ty = LHS->getType();
+  Instruction *InsertAt = Preheader->getTerminator();
+  assert(Ty == RHS->getType() && "icmp operands have different types?");
+  Value *NewLHS = Expander.expandCodeFor(NewLHSS, Ty, InsertAt);
+  Value *NewRHS = Expander.expandCodeFor(RHSS, Ty, InsertAt);
+  return Builder.CreateICmp(Pred, NewLHS, NewRHS);
 }
 
 bool LoopPredication::widenGuardConditions(IntrinsicInst *Guard,
diff --git a/test/Transforms/LoopPredication/basic.ll b/test/Transforms/LoopPredication/basic.ll
index a347e6192bd..6ce07819cb0 100644
--- a/test/Transforms/LoopPredication/basic.ll
+++ b/test/Transforms/LoopPredication/basic.ll
@@ -493,4 +493,79 @@ loop:
 exit:
   %result = phi i32 [ 0, %entry ], [ %loop.acc.next, %loop ]
   ret i32 %result
-}
\ No newline at end of file
+}
+
+define i32 @unsigned_loop_0_to_n_hoist_length(i32* %array, i16 %length.i16, i32 %n) {
+; CHECK-LABEL: @unsigned_loop_0_to_n_hoist_length
+entry:
+  %tmp5 = icmp eq i32 %n, 0
+  br i1 %tmp5, label %exit, label %loop.preheader
+
+loop.preheader:
+; CHECK: loop.preheader:
+; CHECK: [[max_index:[^ ]+]] = add i32 %n, -1
+; CHECK-NEXT: [[length:[^ ]+]] = zext i16 %length.i16 to i32
+; CHECK-NEXT: [[wide_cond:[^ ]+]] = icmp ult i32 [[max_index]], [[length]]
+; CHECK-NEXT: br label %loop
+  br label %loop
+
+loop:
+; CHECK: loop:
+; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 [[wide_cond]], i32 9) [ "deopt"() ]
+  %loop.acc = phi i32 [ %loop.acc.next, %loop ], [ 0, %loop.preheader ]
+  %i = phi i32 [ %i.next, %loop ], [ 0, %loop.preheader ]
+  %length = zext i16 %length.i16 to i32
+  %within.bounds = icmp ult i32 %i, %length
+  call void (i1, ...) @llvm.experimental.guard(i1 %within.bounds, i32 9) [ "deopt"() ]
+
+  %i.i64 = zext i32 %i to i64
+  %array.i.ptr = getelementptr inbounds i32, i32* %array, i64 %i.i64
+  %array.i = load i32, i32* %array.i.ptr, align 4
+  %loop.acc.next = add i32 %loop.acc, %array.i
+
+  %i.next = add nuw i32 %i, 1
+  %continue = icmp ult i32 %i.next, %n
+  br i1 %continue, label %loop, label %exit
+
+exit:
+  %result = phi i32 [ 0, %entry ], [ %loop.acc.next, %loop ]
+  ret i32 %result
+}
+
+define i32 @unsigned_loop_0_to_n_cant_hoist_length(i32* %array, i32 %length, i32 %divider, i32 %n) {
+; CHECK-LABEL: @unsigned_loop_0_to_n_cant_hoist_length
+entry:
+  %tmp5 = icmp eq i32 %n, 0
+  br i1 %tmp5, label %exit, label %loop.preheader
+
+loop.preheader:
+; CHECK: loop.preheader:
+; CHECK-NEXT: br label %loop
+  br label %loop
+
+loop:
+; CHECK: loop:
+; CHECK-NEXT: %loop.acc = phi i32 [ %loop.acc.next, %loop ], [ 0, %loop.preheader ]
+; CHECK-NEXT: %i = phi i32 [ %i.next, %loop ], [ 0, %loop.preheader ]
+; CHECK-NEXT: %length.udiv = udiv i32 %length, %divider
+; CHECK-NEXT: %within.bounds = icmp ult i32 %i, %length.udiv
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %within.bounds, i32 9) [ "deopt"() ]
+  %loop.acc = phi i32 [ %loop.acc.next, %loop ], [ 0, %loop.preheader ]
+  %i = phi i32 [ %i.next, %loop ], [ 0, %loop.preheader ]
+  %length.udiv = udiv i32 %length, %divider
+  %within.bounds = icmp ult i32 %i, %length.udiv
+  call void (i1, ...) @llvm.experimental.guard(i1 %within.bounds, i32 9) [ "deopt"() ]
+
+  %i.i64 = zext i32 %i to i64
+  %array.i.ptr = getelementptr inbounds i32, i32* %array, i64 %i.i64
+  %array.i = load i32, i32* %array.i.ptr, align 4
+  %loop.acc.next = add i32 %loop.acc, %array.i
+
+  %i.next = add nuw i32 %i, 1
+  %continue = icmp ult i32 %i.next, %n
+  br i1 %continue, label %loop, label %exit
+
+exit:
+  %result = phi i32 [ 0, %entry ], [ %loop.acc.next, %loop ]
+  ret i32 %result
+}