From 145eb97d3a8a1f2766a891003c659483dcf15681 Mon Sep 17 00:00:00 2001
From: Quentin Colombet <qcolombet@apple.com>
Date: Wed, 19 Jun 2013 19:59:41 +0000
Subject: [PATCH] LSR: Fix the parameters used to compute the scaling factor
 cost.

Prior to this change, the considered addressing modes may be invalid since the
maximum and minimum offsets were not taking into account.
This was causing an assertion failure.

The added test case exercices that behavior.

<rdar://problem/14199725> Assertion failed: (CurScaleCost >= 0 && "Legal
addressing mode has an illegal cost!")

llvm-svn: 184341
---
 .../Transforms/Scalar/LoopStrengthReduce.cpp  | 18 +++--
 .../scaling_factor_cost_crash.ll              | 68 +++++++++++++++++++
 2 files changed, 81 insertions(+), 5 deletions(-)
 create mode 100644 llvm/test/Transforms/LoopStrengthReduce/scaling_factor_cost_crash.ll

diff --git a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 246de56d9ad2..14cb9793925f 100644
--- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -1417,11 +1417,19 @@ static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
 
   switch (LU.Kind) {
   case LSRUse::Address: {
-    int CurScaleCost = TTI.getScalingFactorCost(LU.AccessTy, F.BaseGV,
-                                                F.BaseOffset, F.HasBaseReg,
-                                                F.Scale);
-    assert(CurScaleCost >= 0 && "Legal addressing mode has an illegal cost!");
-    return CurScaleCost;
+    // Check the scaling factor cost with both the min and max offsets.
+    int ScaleCostMinOffset =
+      TTI.getScalingFactorCost(LU.AccessTy, F.BaseGV,
+                               F.BaseOffset + LU.MinOffset,
+                               F.HasBaseReg, F.Scale);
+    int ScaleCostMaxOffset =
+      TTI.getScalingFactorCost(LU.AccessTy, F.BaseGV,
+                               F.BaseOffset + LU.MaxOffset,
+                               F.HasBaseReg, F.Scale);
+
+    assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 &&
+           "Legal addressing mode has an illegal cost!");
+    return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
   }
   case LSRUse::ICmpZero:
     // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg.
diff --git a/llvm/test/Transforms/LoopStrengthReduce/scaling_factor_cost_crash.ll b/llvm/test/Transforms/LoopStrengthReduce/scaling_factor_cost_crash.ll
new file mode 100644
index 000000000000..cd8fec3d2c81
--- /dev/null
+++ b/llvm/test/Transforms/LoopStrengthReduce/scaling_factor_cost_crash.ll
@@ -0,0 +1,68 @@
+; RUN: opt -loop-reduce %s -S -o - | FileCheck %s
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f80:128:128-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32-S32"
+target triple = "i686-pc-win32"
+
+; <rdar://problem/14199725> Assertion failed: (CurScaleCost >= 0 && "Legal addressing mode has an illegal cost!")
+; CHECK: @scalingFactorCrash
+define void @scalingFactorCrash() {
+  br i1 undef, label %1, label %24
+
+; <label>:1                                       ; preds = %0
+  br i1 undef, label %2, label %24
+
+; <label>:2                                       ; preds = %1
+  br i1 undef, label %3, label %24
+
+; <label>:3                                       ; preds = %2
+  br i1 undef, label %4, label %24
+
+; <label>:4                                       ; preds = %3
+  br i1 undef, label %24, label %6
+
+; <label>:5                                       ; preds = %6
+  br i1 undef, label %24, label %7
+
+; <label>:6                                       ; preds = %6, %4
+  br i1 undef, label %6, label %5
+
+; <label>:7                                       ; preds = %9, %5
+  br label %8
+
+; <label>:8                                       ; preds = %8, %7
+  br i1 undef, label %9, label %8
+
+; <label>:9                                       ; preds = %8
+  br i1 undef, label %7, label %10
+
+; <label>:10                                      ; preds = %9
+  br i1 undef, label %24, label %11
+
+; <label>:11                                      ; preds = %10
+  br i1 undef, label %15, label %13
+
+; <label>:12                                      ; preds = %14
+  br label %15
+
+; <label>:13                                      ; preds = %11
+  br label %14
+
+; <label>:14                                      ; preds = %14, %13
+  br i1 undef, label %14, label %12
+
+; <label>:15                                      ; preds = %12, %11
+  br i1 undef, label %16, label %24
+
+; <label>:16                                      ; preds = %16, %15
+  %17 = phi i32 [ %21, %16 ], [ undef, %15 ]
+  %18 = sub i32 %17, 1623127498
+  %19 = getelementptr inbounds i32* undef, i32 %18
+  store i32 undef, i32* %19, align 4
+  %20 = add i32 %17, 1623127499
+  %21 = add i32 %20, -1623127498
+  %22 = add i32 %21, -542963121
+  %23 = icmp ult i32 %22, undef
+  br i1 undef, label %16, label %24
+
+; <label>:24                                      ; preds = %16, %15, %10, %5, %4, %3, %2, %1, %0
+  ret void
+}