[llvm] [AMDGPU][SplitModule] Fix unintentional integer division (PR #117586)

[Fraser Cormack via llvm-commits]

https://github.com/frasercrmck updated https://github.com/llvm/llvm-project/pull/117586

>From 70ce91dd4632aea58bca0ea25cc83e1a4166fa01 Mon Sep 17 00:00:00 2001
From: Fraser Cormack <fraser at codeplay.com>
Date: Mon, 25 Nov 2024 17:56:50 +0000
Subject: [PATCH 1/2] [AMDGPU][SplitModule] Fix unintentional integer division

A static analysis tool warned that a division was always being performed
in integer division, so was either 0.0 or 1.0.

This doesn't seem intentional, so has been fixed to return a true ratio
using floating-point division. This in turn showed a bug where a
comparison against this ratio was incorrect.
---
 llvm/lib/Target/AMDGPU/AMDGPUSplitModule.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUSplitModule.cpp b/llvm/lib/Target/AMDGPU/AMDGPUSplitModule.cpp
index 5d7aff1c5092cc..6adb43a153999a 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUSplitModule.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUSplitModule.cpp
@@ -1101,9 +1101,9 @@ void RecursiveSearchSplitting::pickPartition(unsigned Depth, unsigned Idx,
         // Check if the amount of code in common makes it worth it.
         assert(SimilarDepsCost && Entry.CostExcludingGraphEntryPoints);
         const double Ratio =
-            SimilarDepsCost / Entry.CostExcludingGraphEntryPoints;
+            (double)SimilarDepsCost / Entry.CostExcludingGraphEntryPoints;
         assert(Ratio >= 0.0 && Ratio <= 1.0);
-        if (LargeFnOverlapForMerge > Ratio) {
+        if (Ratio > LargeFnOverlapForMerge) {
           // For debug, just print "L", so we'll see "L3=P3" for instance, which
           // will mean we reached max depth and chose P3 based on this
           // heuristic.

>From cdecbbcbdb1618902179bba7f97947856977e83e Mon Sep 17 00:00:00 2001
From: Fraser Cormack <fraser at codeplay.com>
Date: Tue, 26 Nov 2024 16:03:31 +0000
Subject: [PATCH 2/2] static_cast

---
 llvm/lib/Target/AMDGPU/AMDGPUSplitModule.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUSplitModule.cpp b/llvm/lib/Target/AMDGPU/AMDGPUSplitModule.cpp
index 6adb43a153999a..6f1c45d92c8cb2 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUSplitModule.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUSplitModule.cpp
@@ -1100,8 +1100,8 @@ void RecursiveSearchSplitting::pickPartition(unsigned Depth, unsigned Idx,
       if (Entry.CostExcludingGraphEntryPoints > LargeClusterThreshold) {
         // Check if the amount of code in common makes it worth it.
         assert(SimilarDepsCost && Entry.CostExcludingGraphEntryPoints);
-        const double Ratio =
-            (double)SimilarDepsCost / Entry.CostExcludingGraphEntryPoints;
+        const double Ratio = static_cast<double>(SimilarDepsCost) /
+                             Entry.CostExcludingGraphEntryPoints;
         assert(Ratio >= 0.0 && Ratio <= 1.0);
         if (Ratio > LargeFnOverlapForMerge) {
           // For debug, just print "L", so we'll see "L3=P3" for instance, which