return simplifyInstWithSCEV(&I);
}
- /// TODO: Add visitors for other instruction types, e.g. ZExt, SExt.
-
/// Try to simplify binary operator I.
///
/// TODO: Probaly it's worth to hoist the code for estimating the
return Base::visitCastInst(I);
}
+
+ bool visitCmpInst(CmpInst &I) {
+ Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
+
+ // First try to handle simplified comparisons.
+ if (!isa<Constant>(LHS))
+ if (Constant *SimpleLHS = SimplifiedValues.lookup(LHS))
+ LHS = SimpleLHS;
+ if (!isa<Constant>(RHS))
+ if (Constant *SimpleRHS = SimplifiedValues.lookup(RHS))
+ RHS = SimpleRHS;
+
+ if (!isa<Constant>(LHS) && !isa<Constant>(RHS)) {
+ auto SimplifiedLHS = SimplifiedAddresses.find(LHS);
+ if (SimplifiedLHS != SimplifiedAddresses.end()) {
+ auto SimplifiedRHS = SimplifiedAddresses.find(RHS);
+ if (SimplifiedRHS != SimplifiedAddresses.end()) {
+ SimplifiedAddress &LHSAddr = SimplifiedLHS->second;
+ SimplifiedAddress &RHSAddr = SimplifiedRHS->second;
+ if (LHSAddr.Base == RHSAddr.Base) {
+ LHS = LHSAddr.Offset;
+ RHS = RHSAddr.Offset;
+ }
+ }
+ }
+ }
+
+ if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
+ if (Constant *CRHS = dyn_cast<Constant>(RHS)) {
+ if (Constant *C = ConstantExpr::getCompare(I.getPredicate(), CLHS, CRHS)) {
+ SimplifiedValues[&I] = C;
+ return true;
+ }
+ }
+ }
+
+ return Base::visitCmpInst(I);
+ }
};
} // namespace
return None;
}
+ TerminatorInst *TI = BB->getTerminator();
+
+ // Add in the live successors by first checking whether we have terminator
+ // that may be simplified based on the values simplified by this call.
+ if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
+ if (BI->isConditional()) {
+ if (Constant *SimpleCond =
+ SimplifiedValues.lookup(BI->getCondition())) {
+ BBWorklist.insert(BI->getSuccessor(
+ cast<ConstantInt>(SimpleCond)->isZero() ? 1 : 0));
+ continue;
+ }
+ }
+ } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ if (Constant *SimpleCond =
+ SimplifiedValues.lookup(SI->getCondition())) {
+ BBWorklist.insert(
+ SI->getSuccessor(cast<ConstantInt>(SimpleCond)->getSExtValue()));
+ continue;
+ }
+ }
+
// Add BB's successors to the worklist.
for (BasicBlock *Succ : successors(BB))
if (L->contains(Succ))
--- /dev/null
+; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=100 -unroll-dynamic-cost-savings-discount=1000 -unroll-threshold=10 -unroll-percent-dynamic-cost-saved-threshold=50 | FileCheck %s
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+@known_constant = internal unnamed_addr constant [10 x i32] [i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1], align 16
+
+; We should be able to propagate constant data through comparisons.
+; For example, in this test we have a load, which becomes constant after
+; unrolling, making comparison with 0 also known to be 0 (false) - and that
+; will trigger further simplifications.
+;
+; We expect this loop to be unrolled, because in this case load would become
+; constant, which is always 1, and which, in its turn, helps to simplify
+; following comparison, zero-extension, and addition. In total, unrolling should help to
+; optimize more than 50% of all instructions in this case.
+;
+; CHECK-LABEL: @const_compare
+; CHECK-NOT: br i1 %
+; CHECK: ret i32
+define i32 @const_compare(i32* noalias nocapture readonly %b) {
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.inc, %entry
+ %iv.0 = phi i64 [ 0, %entry ], [ %iv.1, %for.body ]
+ %r.0 = phi i32 [ 0, %entry ], [ %r.1, %for.body ]
+ %arrayidx1 = getelementptr inbounds [10 x i32], [10 x i32]* @known_constant, i64 0, i64 %iv.0
+ %x1 = load i32, i32* %arrayidx1, align 4
+ %cmp = icmp eq i32 %x1, 0
+ %cast = zext i1 %cmp to i32
+ %iv.1 = add nuw nsw i64 %iv.0, 1
+ %r.1 = add i32 %r.0, %cast
+ %exitcond = icmp eq i64 %iv.1, 10
+ br i1 %exitcond, label %for.end, label %for.body
+
+for.end: ; preds = %for.inc
+ ret i32 %r.1
+}
+
+; If we can figure out result of comparison on each iteration, we can resolve
+; the depending branch. That means, that the unrolled version of the loop would
+; have less code, because we don't need not-taken basic blocks there.
+; This test checks that this is taken into consideration.
+; We expect this loop to be unrolled, because the most complicated part of its
+; body (if.then block) is never actually executed.
+; CHECK-LABEL: @branch_folded
+; CHECK-NOT: br i1 %
+; CHECK: ret i32
+define i32 @branch_folded(i32* noalias nocapture readonly %b) {
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.inc, %entry
+ %iv.0 = phi i64 [ 0, %entry ], [ %iv.1, %for.inc ]
+ %r.0 = phi i32 [ 0, %entry ], [ %r.1, %for.inc ]
+ %arrayidx1 = getelementptr inbounds [10 x i32], [10 x i32]* @known_constant, i64 0, i64 %iv.0
+ %x1 = load i32, i32* %arrayidx1, align 4
+ %cmp = icmp eq i32 %x1, 0
+ %iv.1 = add nuw nsw i64 %iv.0, 1
+ br i1 %cmp, label %if.then, label %for.inc
+
+if.then: ; preds = %for.body
+ %arrayidx2 = getelementptr inbounds i32, i32* %b, i64 %iv.0
+ %x2 = load i32, i32* %arrayidx2, align 4
+ %add = add nsw i32 %x2, %r.0
+ br label %for.inc
+
+for.inc: ; preds = %for.body, %if.then
+ %r.1 = phi i32 [ %add, %if.then ], [ %x1, %for.body ]
+ %exitcond = icmp eq i64 %iv.1, 10
+ br i1 %exitcond, label %for.end, label %for.body
+
+for.end: ; preds = %for.inc
+ ret i32 %r.1
+}
+
+; This test is similar to the previous one, but in this we use IV in comparison
+; (not a loaded value as we did there).
+; CHECK-LABEL: @branch_iv
+; CHECK-NOT: br i1 %
+; CHECK: ret i64
+define i64 @branch_iv(i64* noalias nocapture readonly %b) {
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.inc, %entry
+ %indvars.iv = phi i64 [ 0, %entry ], [ %tmp3, %for.inc ]
+ %r.030 = phi i64 [ 0, %entry ], [ %r.1, %for.inc ]
+ %cmp3 = icmp eq i64 %indvars.iv, 5
+ %tmp3 = add nuw nsw i64 %indvars.iv, 1
+ br i1 %cmp3, label %if.then, label %for.inc
+
+if.then: ; preds = %for.body
+ %arrayidx2 = getelementptr inbounds i64, i64* %b, i64 %tmp3
+ %tmp1 = load i64, i64* %arrayidx2, align 4
+ %add = add nsw i64 %tmp1, %r.030
+ br label %for.inc
+
+for.inc: ; preds = %if.then, %for.body
+ %r.1 = phi i64 [ %add, %if.then ], [ %r.030, %for.body ]
+ %exitcond = icmp eq i64 %tmp3, 20
+ br i1 %exitcond, label %for.end, label %for.body
+
+for.end: ; preds = %for.inc
+ ret i64 %r.1
+}
+
+; Induction variables are often casted to another type, and that shouldn't
+; prevent us from folding branches. Tthis test specifically checks if we can
+; handle this. Other than thatm it's similar to the previous test.
+; CHECK-LABEL: @branch_iv_trunc
+; CHECK-NOT: br i1 %
+; CHECK: ret i32
+define i32 @branch_iv_trunc(i32* noalias nocapture readonly %b) {
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.inc, %entry
+ %indvars.iv = phi i64 [ 0, %entry ], [ %tmp3, %for.inc ]
+ %r.030 = phi i32 [ 0, %entry ], [ %r.1, %for.inc ]
+ %tmp2 = trunc i64 %indvars.iv to i32
+ %cmp3 = icmp eq i32 %tmp2, 5
+ %tmp3 = add nuw nsw i64 %indvars.iv, 1
+ br i1 %cmp3, label %if.then, label %for.inc
+
+if.then: ; preds = %for.body
+ %arrayidx2 = getelementptr inbounds i32, i32* %b, i64 %tmp3
+ %tmp1 = load i32, i32* %arrayidx2, align 4
+ %add = add nsw i32 %tmp1, %r.030
+ br label %for.inc
+
+for.inc: ; preds = %if.then, %for.body
+ %r.1 = phi i32 [ %add, %if.then ], [ %r.030, %for.body ]
+ %exitcond = icmp eq i64 %tmp3, 10
+ br i1 %exitcond, label %for.end, label %for.body
+
+for.end: ; preds = %for.inc
+ ret i32 %r.1
+}
+
+; Check that we don't crash when we analyze icmp with pointer-typed IV and a
+; pointer.
+; CHECK-LABEL: @ptr_cmp_crash
+; CHECK: ret void
+define void @ptr_cmp_crash() {
+entry:
+ br label %while.body
+
+while.body:
+ %iv.0 = phi i32* [ getelementptr inbounds ([10 x i32], [10 x i32]* @known_constant, i64 0, i64 0), %entry ], [ %iv.1, %while.body ]
+ %iv.1 = getelementptr inbounds i32, i32* %iv.0, i64 1
+ %exitcond = icmp eq i32* %iv.1, getelementptr inbounds ([10 x i32], [10 x i32]* @known_constant, i64 0, i64 9)
+ br i1 %exitcond, label %loop.exit, label %while.body
+
+loop.exit:
+ ret void
+}
+
+; Check that we don't crash when we analyze ptrtoint cast.
+; CHECK-LABEL: @ptrtoint_cast_crash
+; CHECK: ret void
+define void @ptrtoint_cast_crash(i8 * %a) {
+entry:
+ %limit = getelementptr i8, i8* %a, i64 512
+ br label %loop.body
+
+loop.body:
+ %iv.0 = phi i8* [ %a, %entry ], [ %iv.1, %loop.body ]
+ %cast = ptrtoint i8* %iv.0 to i64
+ %iv.1 = getelementptr inbounds i8, i8* %iv.0, i64 1
+ %exitcond = icmp ne i8* %iv.1, %limit
+ br i1 %exitcond, label %loop.body, label %loop.exit
+
+loop.exit:
+ ret void
+}
+
+; Loop unroller should be able to predict that a comparison would become
+; constant if the operands are pointers with the same base and constant
+; offsets.
+; We expect this loop to be unrolled, since most of its instructions would
+; become constant after it.
+; CHECK-LABEL: @ptr_cmp
+; CHECK-NOT: br i1 %
+; CHECK: ret i64
+define i64 @ptr_cmp(i8 * %a) {
+entry:
+ %limit = getelementptr i8, i8* %a, i64 40
+ %start.iv2 = getelementptr i8, i8* %a, i64 7
+ br label %loop.body
+
+loop.body:
+ %iv.0 = phi i8* [ %a, %entry ], [ %iv.1, %loop.body ]
+ %iv2.0 = phi i8* [ %start.iv2, %entry ], [ %iv2.1, %loop.body ]
+ %r.0 = phi i64 [ 0, %entry ], [ %r.1, %loop.body ]
+ %cast = ptrtoint i8* %iv.0 to i64
+ %cmp = icmp eq i8* %iv2.0, %iv.0
+ %sub = sext i1 %cmp to i64
+ %mul = mul i64 %sub, %cast
+ %r.1 = add i64 %r.0, %mul
+ %iv.1 = getelementptr inbounds i8, i8* %iv.0, i64 1
+ %iv2.1 = getelementptr inbounds i8, i8* %iv2.0, i64 1
+ %exitcond = icmp ne i8* %iv.1, %limit
+ br i1 %exitcond, label %loop.body, label %loop.exit
+
+loop.exit:
+ ret i64 %r.1
+}