[llvm-commits] [llvm] r101068 - in /llvm/trunk: lib/Transforms/Scalar/IndVarSimplify.cpp test/Transforms/IndVarSimplify/udiv.ll
Dan Gohman
gohman at apple.com
Mon Apr 12 14:13:43 PDT 2010
Author: djg
Date: Mon Apr 12 16:13:43 2010
New Revision: 101068
URL: http://llvm.org/viewvc/llvm-project?rev=101068&view=rev
Log:
Suppress LinearFunctionTestReplace when the computed backedge-taken
expression is a UDiv and it doesn't appear that the UDiv came from
the user's source.
ScalarEvolution has recently figured out how to compute a tripcount
expression for the inner loop in
SingleSource/Benchmarks/Shootout/sieve.c, using a udiv. Emitting a
udiv instruction dramatically slows down the enclosing loop.
Added:
llvm/trunk/test/Transforms/IndVarSimplify/udiv.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp?rev=101068&r1=101067&r2=101068&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp Mon Apr 12 16:13:43 2010
@@ -134,6 +134,24 @@
BasicBlock *ExitingBlock,
BranchInst *BI,
SCEVExpander &Rewriter) {
+ // Special case: If the backedge-taken count is a UDiv, it's very likely a
+ // UDiv that ScalarEvolution produced in order to compute a precise
+ // expression, rather than a UDiv from the user's code. If we can't find a
+ // UDiv in the code with some simple searching, assume the former and forego
+ // rewriting the loop.
+ if (isa<SCEVUDivExpr>(BackedgeTakenCount)) {
+ ICmpInst *OrigCond = dyn_cast<ICmpInst>(BI->getCondition());
+ if (!OrigCond) return 0;
+ const SCEV *R = SE->getSCEV(OrigCond->getOperand(1));
+ R = SE->getMinusSCEV(R, SE->getIntegerSCEV(1, R->getType()));
+ if (R != BackedgeTakenCount) {
+ const SCEV *L = SE->getSCEV(OrigCond->getOperand(0));
+ L = SE->getMinusSCEV(L, SE->getIntegerSCEV(1, L->getType()));
+ if (L != BackedgeTakenCount)
+ return 0;
+ }
+ }
+
// If the exiting block is not the same as the backedge block, we must compare
// against the preincremented value, otherwise we prefer to compare against
// the post-incremented value.
Added: llvm/trunk/test/Transforms/IndVarSimplify/udiv.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/udiv.ll?rev=101068&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/udiv.ll (added)
+++ llvm/trunk/test/Transforms/IndVarSimplify/udiv.ll Mon Apr 12 16:13:43 2010
@@ -0,0 +1,162 @@
+; RUN: opt -indvars -S < %s | FileCheck %s
+
+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-n8:16:32:64"
+
+ at main.flags = internal global [8193 x i8] zeroinitializer, align 1 ; <[8193 x i8]*> [#uses=5]
+ at .str = private constant [11 x i8] c"Count: %d\0A\00" ; <[11 x i8]*> [#uses=1]
+
+; Indvars shouldn't emit a udiv here, because there's no udiv in the
+; original code. This comes from SingleSource/Benchmarks/Shootout/sieve.c.
+
+; CHECK: @main
+; CHECK-NOT: div
+
+define i32 @main(i32 %argc, i8** nocapture %argv) nounwind {
+entry:
+ %cmp = icmp eq i32 %argc, 2 ; <i1> [#uses=1]
+ br i1 %cmp, label %cond.true, label %while.cond.preheader
+
+cond.true: ; preds = %entry
+ %arrayidx = getelementptr inbounds i8** %argv, i64 1 ; <i8**> [#uses=1]
+ %tmp2 = load i8** %arrayidx ; <i8*> [#uses=1]
+ %call = tail call i32 @atoi(i8* %tmp2) nounwind readonly ; <i32> [#uses=1]
+ br label %while.cond.preheader
+
+while.cond.preheader: ; preds = %entry, %cond.true
+ %NUM.0.ph = phi i32 [ %call, %cond.true ], [ 170000, %entry ] ; <i32> [#uses=2]
+ %tobool18 = icmp eq i32 %NUM.0.ph, 0 ; <i1> [#uses=1]
+ br i1 %tobool18, label %while.end, label %bb.nph30
+
+while.cond.loopexit: ; preds = %for.cond12.while.cond.loopexit_crit_edge, %for.cond12.loopexit
+ %count.2.lcssa = phi i32 [ %count.1.lcssa, %for.cond12.while.cond.loopexit_crit_edge ], [ 0, %for.cond12.loopexit ] ; <i32> [#uses=1]
+ br label %while.cond
+
+while.cond: ; preds = %while.cond.loopexit
+ %tobool = icmp eq i32 %dec19, 0 ; <i1> [#uses=1]
+ br i1 %tobool, label %while.cond.while.end_crit_edge, label %for.cond.preheader
+
+while.cond.while.end_crit_edge: ; preds = %while.cond
+ %count.2.lcssa.lcssa = phi i32 [ %count.2.lcssa, %while.cond ] ; <i32> [#uses=1]
+ br label %while.end
+
+bb.nph30: ; preds = %while.cond.preheader
+ br label %for.cond.preheader
+
+for.cond.preheader: ; preds = %bb.nph30, %while.cond
+ %dec19.in = phi i32 [ %NUM.0.ph, %bb.nph30 ], [ %dec19, %while.cond ] ; <i32> [#uses=1]
+ %dec19 = add i32 %dec19.in, -1 ; <i32> [#uses=2]
+ br i1 true, label %bb.nph, label %for.cond12.loopexit
+
+for.cond: ; preds = %for.body
+ %cmp8 = icmp slt i64 %inc, 8193 ; <i1> [#uses=1]
+ br i1 %cmp8, label %for.body, label %for.cond.for.cond12.loopexit_crit_edge
+
+for.cond.for.cond12.loopexit_crit_edge: ; preds = %for.cond
+ br label %for.cond12.loopexit
+
+bb.nph: ; preds = %for.cond.preheader
+ br label %for.body
+
+for.body: ; preds = %bb.nph, %for.cond
+ %i.02 = phi i64 [ 2, %bb.nph ], [ %inc, %for.cond ] ; <i64> [#uses=2]
+ %arrayidx10 = getelementptr inbounds [8193 x i8]* @main.flags, i64 0, i64 %i.02 ; <i8*> [#uses=1]
+ store i8 1, i8* %arrayidx10
+ %inc = add nsw i64 %i.02, 1 ; <i64> [#uses=2]
+ br label %for.cond
+
+for.cond12.loopexit: ; preds = %for.cond.for.cond12.loopexit_crit_edge, %for.cond.preheader
+ br i1 true, label %bb.nph16, label %while.cond.loopexit
+
+for.cond12: ; preds = %for.inc35
+ %cmp14 = icmp slt i64 %inc37, 8193 ; <i1> [#uses=1]
+ br i1 %cmp14, label %for.body15, label %for.cond12.while.cond.loopexit_crit_edge
+
+for.cond12.while.cond.loopexit_crit_edge: ; preds = %for.cond12
+ %count.1.lcssa = phi i32 [ %count.1, %for.cond12 ] ; <i32> [#uses=1]
+ br label %while.cond.loopexit
+
+bb.nph16: ; preds = %for.cond12.loopexit
+ br label %for.body15
+
+for.body15: ; preds = %bb.nph16, %for.cond12
+ %count.212 = phi i32 [ 0, %bb.nph16 ], [ %count.1, %for.cond12 ] ; <i32> [#uses=2]
+ %i.17 = phi i64 [ 2, %bb.nph16 ], [ %inc37, %for.cond12 ] ; <i64> [#uses=4]
+ %arrayidx17 = getelementptr inbounds [8193 x i8]* @main.flags, i64 0, i64 %i.17 ; <i8*> [#uses=1]
+ %tmp18 = load i8* %arrayidx17 ; <i8> [#uses=1]
+ %tobool19 = icmp eq i8 %tmp18, 0 ; <i1> [#uses=1]
+ br i1 %tobool19, label %for.inc35, label %if.then
+
+if.then: ; preds = %for.body15
+ %add = shl i64 %i.17, 1 ; <i64> [#uses=2]
+ %cmp243 = icmp slt i64 %add, 8193 ; <i1> [#uses=1]
+ br i1 %cmp243, label %bb.nph5, label %for.end32
+
+for.cond22: ; preds = %for.body25
+ %cmp24 = icmp slt i64 %add31, 8193 ; <i1> [#uses=1]
+ br i1 %cmp24, label %for.body25, label %for.cond22.for.end32_crit_edge
+
+for.cond22.for.end32_crit_edge: ; preds = %for.cond22
+ br label %for.end32
+
+bb.nph5: ; preds = %if.then
+ br label %for.body25
+
+for.body25: ; preds = %bb.nph5, %for.cond22
+ %k.04 = phi i64 [ %add, %bb.nph5 ], [ %add31, %for.cond22 ] ; <i64> [#uses=2]
+ %arrayidx27 = getelementptr inbounds [8193 x i8]* @main.flags, i64 0, i64 %k.04 ; <i8*> [#uses=1]
+ store i8 0, i8* %arrayidx27
+ %add31 = add nsw i64 %k.04, %i.17 ; <i64> [#uses=2]
+ br label %for.cond22
+
+for.end32: ; preds = %for.cond22.for.end32_crit_edge, %if.then
+ %inc34 = add nsw i32 %count.212, 1 ; <i32> [#uses=1]
+ br label %for.inc35
+
+for.inc35: ; preds = %for.body15, %for.end32
+ %count.1 = phi i32 [ %inc34, %for.end32 ], [ %count.212, %for.body15 ] ; <i32> [#uses=2]
+ %inc37 = add nsw i64 %i.17, 1 ; <i64> [#uses=2]
+ br label %for.cond12
+
+while.end: ; preds = %while.cond.while.end_crit_edge, %while.cond.preheader
+ %count.0.lcssa = phi i32 [ %count.2.lcssa.lcssa, %while.cond.while.end_crit_edge ], [ 0, %while.cond.preheader ] ; <i32> [#uses=1]
+ %call40 = tail call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([11 x i8]* @.str, i64 0, i64 0), i32 %count.0.lcssa) nounwind ; <i32> [#uses=0]
+ ret i32 0
+}
+
+declare i32 @atoi(i8* nocapture) nounwind readonly
+
+declare i32 @printf(i8* nocapture, ...) nounwind
+
+; IndVars shouldn't be afraid to emit a udiv here, since there's a udiv in
+; the original code.
+
+; CHECK: @foo
+; CHECK: for.body.preheader:
+; CHECK-NEXT: udiv
+
+define void @foo(double* %p, i64 %n) nounwind {
+entry:
+ %div0 = udiv i64 %n, 7 ; <i64> [#uses=1]
+ %div1 = add i64 %div0, 1
+ %cmp2 = icmp ult i64 0, %div1 ; <i1> [#uses=1]
+ br i1 %cmp2, label %for.body.preheader, label %for.end
+
+for.body.preheader: ; preds = %entry
+ br label %for.body
+
+for.body: ; preds = %for.body.preheader, %for.body
+ %i.03 = phi i64 [ %inc, %for.body ], [ 0, %for.body.preheader ] ; <i64> [#uses=2]
+ %arrayidx = getelementptr inbounds double* %p, i64 %i.03 ; <double*> [#uses=1]
+ store double 0.000000e+00, double* %arrayidx
+ %inc = add i64 %i.03, 1 ; <i64> [#uses=2]
+ %divx = udiv i64 %n, 7 ; <i64> [#uses=1]
+ %div = add i64 %divx, 1
+ %cmp = icmp ult i64 %inc, %div ; <i1> [#uses=1]
+ br i1 %cmp, label %for.body, label %for.end.loopexit
+
+for.end.loopexit: ; preds = %for.body
+ br label %for.end
+
+for.end: ; preds = %for.end.loopexit, %entry
+ ret void
+}
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