[llvm] [PPC][NFC] add an option for GatherAllAliasesMaxDepth (PR #87071)

[Chen Zheng via llvm-commits]

https://github.com/chenzheng1030 created https://github.com/llvm/llvm-project/pull/87071

GatherAllAliases is time consuming. Add an debug option on PPC to control the complexity of the function. This is useful when debuging compile time related issues.

>From 0224b887bad85094f82c291db3b28564821d2fd7 Mon Sep 17 00:00:00 2001
From: Chen Zheng <czhengsz at cn.ibm.com>
Date: Fri, 29 Mar 2024 10:12:40 -0400
Subject: [PATCH] [PPC][NFC] add an option for GatherAllAliasesMaxDepth

GatherAllAliases is time consuming. Add an debug option on PPC to
control the complexity of the function. This is useful when debuging
compile time related issues.
---
 llvm/lib/Target/PowerPC/PPCISelLowering.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 7436b202fba0d9..43e4a34a9b3483 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -137,6 +137,10 @@ static cl::opt<unsigned> PPCMinimumJumpTableEntries(
     "ppc-min-jump-table-entries", cl::init(64), cl::Hidden,
     cl::desc("Set minimum number of entries to use a jump table on PPC"));
 
+static cl::opt<unsigned> PPCGatherAllAliasesMaxDepth(
+    "ppc-gather-alias-max-depth", cl::init(18), cl::Hidden,
+    cl::desc("max depth when checking alias info in GatherAllAliases()"));
+
 STATISTIC(NumTailCalls, "Number of tail calls");
 STATISTIC(NumSiblingCalls, "Number of sibling calls");
 STATISTIC(ShufflesHandledWithVPERM,
@@ -1512,6 +1516,8 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
   // than the corresponding branch. This information is used in CGP to decide
   // when to convert selects into branches.
   PredictableSelectIsExpensive = Subtarget.isPredictableSelectIsExpensive();
+
+  GatherAllAliasesMaxDepth = PPCGatherAllAliasesMaxDepth;
 }
 
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