llvm.org GIT mirror llvm / 71997f3
Teach IVUsers to stop at non-affine expressions unless they are both outside the loop and reducible. This more completely hides them from LSR, which isn't usually able to do anything meaningful with non-affine expressions anyway, and this consequently hides them from SCEVExpander, which is acutely unprepared for non-affine expressions. Replace test/CodeGen/X86/lsr-nonaffine.ll with a new test that tests the new behavior. This works around the bug in PR10117 / rdar://problem/9633149, and is generally an improvement besides. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134268 91177308-0d34-0410-b5e6-96231b3b80d8 Dan Gohman 8 years ago
2 changed file(s) with 35 addition(s) and 25 deletion(s). Raw diff Collapse all Expand all
4545 /// used by the given expression, within the context of analyzing the
4646 /// given loop.
4747 static bool isInteresting(const SCEV *S, const Instruction *I, const Loop *L,
48 ScalarEvolution *SE) {
48 ScalarEvolution *SE, LoopInfo *LI) {
4949 // An addrec is interesting if it's affine or if it has an interesting start.
5050 if (const SCEVAddRecExpr *AR = dyn_cast(S)) {
51 // Keep things simple. Don't touch loop-variant strides.
51 // Keep things simple. Don't touch loop-variant strides unless they're
52 // only used outside the loop and we can simplify them.
5253 if (AR->getLoop() == L)
53 return AR->isAffine() || !L->contains(I);
54 return AR->isAffine() ||
55 (!L->contains(I) &&
56 SE->getSCEVAtScope(AR, LI->getLoopFor(I->getParent())) != AR);
5457 // Otherwise recurse to see if the start value is interesting, and that
5558 // the step value is not interesting, since we don't yet know how to
5659 // do effective SCEV expansions for addrecs with interesting steps.
57 return isInteresting(AR->getStart(), I, L, SE) &&
58 !isInteresting(AR->getStepRecurrence(*SE), I, L, SE);
60 return isInteresting(AR->getStart(), I, L, SE, LI) &&
61 !isInteresting(AR->getStepRecurrence(*SE), I, L, SE, LI);
5962 }
6063
6164 // An add is interesting if exactly one of its operands is interesting.
6366 bool AnyInterestingYet = false;
6467 for (SCEVAddExpr::op_iterator OI = Add->op_begin(), OE = Add->op_end();
6568 OI != OE; ++OI)
66 if (isInteresting(*OI, I, L, SE)) {
69 if (isInteresting(*OI, I, L, SE, LI)) {
6770 if (AnyInterestingYet)
6871 return false;
6972 AnyInterestingYet = true;
97100
98101 // If we've come to an uninteresting expression, stop the traversal and
99102 // call this a user.
100 if (!isInteresting(ISE, I, L, SE))
103 if (!isInteresting(ISE, I, L, SE, LI))
101104 return false;
102105
103106 SmallPtrSet UniqueUsers;
None ; RUN: llc -march=x86-64 < %s | FileCheck %s
0 ; RUN: llc -asm-verbose=false -march=x86-64 -o - < %s | FileCheck %s
11
2 ; LSR should compute the correct starting values for this loop. Note that
3 ; it's not necessarily LSR's job to compute loop exit expressions; that's
4 ; indvars' job.
5 ; CHECK: movl $12
6 ; CHECK: movl $42
2 ; LSR should leave non-affine expressions alone because it currently
3 ; doesn't know how to do anything with them, and when it tries, it
4 ; gets SCEVExpander's current expansion for them, which is suboptimal.
75
8 define i32 @real_symmetric_eigen(i32 %n) nounwind {
9 while.body127: ; preds = %while.cond122
10 br label %while.cond141
6 ; CHECK: xorl %eax, %eax
7 ; CHECK-NEXT: align
8 ; CHECK-NEXT: BB0_1:
9 ; CHECK-NEXT: movq %rax, (%rdx)
10 ; CHECK-NEXT: addq %rsi, %rax
11 ; CHECK-NEXT: cmpq %rdi, %rax
12 ; CHECK-NEXT: jl
13 ; CHECK-NEXT: imulq %rax, %rax
14 ; CHECK-NEXT: ret
15 define i64 @foo(i64 %n, i64 %s, i64* %p) nounwind {
16 entry:
17 br label %loop
1118
12 while.cond141: ; preds = %while.cond141, %while.body127
13 %0 = phi i32 [ 7, %while.body127 ], [ %indvar.next67, %while.cond141 ] ; [#uses=3]
14 %indvar.next67 = add i32 %0, 1 ; [#uses=1]
15 %t = icmp slt i32 %indvar.next67, %n
16 br i1 %t, label %if.then171, label %while.cond141
19 loop:
20 %i = phi i64 [ 0, %entry ], [ %i.next, %loop ]
21 volatile store i64 %i, i64* %p
22 %i.next = add i64 %i, %s
23 %c = icmp slt i64 %i.next, %n
24 br i1 %c, label %loop, label %exit
1725
18 if.then171: ; preds = %while.cond141
19 %mul150 = mul i32 %0, %0 ; [#uses=1]
20 %add174 = add i32 %mul150, %0 ; [#uses=1]
21 ret i32 %add174
26 exit:
27 %mul = mul i64 %i.next, %i.next
28 ret i64 %mul
2229 }