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Don't use floating point to do an integer's job.

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This code makes different decisions when compiled into x87 instructions
because of different rounding behavior.  That caused phase 2/3
miscompares on 32-bit Linux when the phase 1 compiler was built with gcc
(using x87), and the phase 2 compiler was built with clang (using SSE).

This fixes PR11200.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143006 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2011-10-26 01:47:48 +00:00
parent 73b5bb3865
commit 794439183a
1 changed files with 7 additions and 4 deletions
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11
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
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@ -2034,14 +2034,17 @@ bool SelectionDAGBuilder::handleJTSwitchCase(CaseRec &CR,
return false;
APInt Range = ComputeRange(First, Last);
double Density = TSize.roundToDouble() / Range.roundToDouble();
if (Density < 0.4)
// The density is TSize / Range. Require at least 40%.
// It should not be possible for IntTSize to saturate for sane code, but make
// sure we handle Range saturation correctly.
uint64_t IntRange = Range.getLimitedValue(UINT64_MAX/10);
uint64_t IntTSize = TSize.getLimitedValue(UINT64_MAX/10);
if (IntTSize * 10 < IntRange * 4)
return false;
DEBUG(dbgs() << "Lowering jump table\n"
<< "First entry: " << First << ". Last entry: " << Last << '\n'
<< "Range: " << Range
<< ". Size: " << TSize << ". Density: " << Density << "\n\n");
<< "Range: " << Range << ". Size: " << TSize << ".\n\n");
// Get the MachineFunction which holds the current MBB. This is used when
// inserting any additional MBBs necessary to represent the switch.