From 82fec4e31da93f17cf95b1bf3f8a0e6d933b4f73 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Thu, 13 May 2004 20:43:31 +0000
Subject: [PATCH] Fix a nasty bug that caused us to unroll EXTREMELY large
loops due to overflow in the size calculation.
This is not something you want to see:
Loop Unroll: F[main] Loop %no_exit Loop Size = 2 Trip Count = 2147483648 - UNROLLING!
The problem was that 2*2147483648 == 0.
Now we get:
Loop Unroll: F[main] Loop %no_exit Loop Size = 2 Trip Count = 2147483648 - TOO LARGE: 4294967296>100
Thanks to some anonymous person playing with the demo page that repeatedly
caused zion to go into swapping land. That's one way to ensure you'll get
a quick bugfix. :)
Testcase here: Transforms/LoopUnroll/2004-05-13-DontUnrollTooMuch.ll
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@13564 91177308-0d34-0410-b5e6-96231b3b80d8
---
lib/Transforms/Scalar/InstructionCombining.cpp | 7 +++++++
lib/Transforms/Scalar/LoopUnroll.cpp | 6 +++---
2 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 67b99c56e7e..7ef1b560477 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -1475,6 +1475,13 @@ Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
// integers at the end of their ranges...
//
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
+ if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
+ if (LHSI->getOpcode() == Instruction::Div && LHSI->hasOneUse() &&
+ isa<ConstantInt>(LHSI->getOperand(1))) {
+ std::cerr << "COULD FOLD: " << *LHSI;
+ std::cerr << "COULD FOLD: " << I << "\n";
+ }
+
// Simplify seteq and setne instructions...
if (I.getOpcode() == Instruction::SetEQ ||
I.getOpcode() == Instruction::SetNE) {
diff --git a/lib/Transforms/Scalar/LoopUnroll.cpp b/lib/Transforms/Scalar/LoopUnroll.cpp
index 33148200b46..a9cced5ce14 100644
--- a/lib/Transforms/Scalar/LoopUnroll.cpp
+++ b/lib/Transforms/Scalar/LoopUnroll.cpp
@@ -139,9 +139,9 @@ bool LoopUnroll::visitLoop(Loop *L) {
DEBUG(std::cerr << "Loop Unroll: F[" << BB->getParent()->getName()
<< "] Loop %" << BB->getName() << " Loop Size = " << LoopSize
<< " Trip Count = " << TripCount << " - ");
- if (LoopSize*TripCount > UnrollThreshold) {
- DEBUG(std::cerr << "TOO LARGE: " << LoopSize*TripCount << ">"
- << UnrollThreshold << "\n");
+ uint64_t Size = (uint64_t)LoopSize*(uint64_t)TripCount;
+ if (Size > UnrollThreshold) {
+ DEBUG(std::cerr << "TOO LARGE: " << Size << ">" << UnrollThreshold << "\n");
return Changed;
}
DEBUG(std::cerr << "UNROLLING!\n");