[PATCH] D26088: Don't leave unused divs/rems sitting around in BypassSlowDivision.
Justin Lebar via llvm-commits
llvm-commits at lists.llvm.org
Fri Oct 28 14:53:30 PDT 2016
This revision was automatically updated to reflect the committed changes.
jlebar marked an inline comment as done.
Closed by commit rL285460: Don't leave unused divs/rems sitting around in BypassSlowDivision. (authored by jlebar).
Changed prior to commit:
https://reviews.llvm.org/D26088?vs=76243&id=76252#toc
Repository:
rL LLVM
https://reviews.llvm.org/D26088
Files:
llvm/trunk/lib/Transforms/Utils/BypassSlowDivision.cpp
llvm/trunk/test/Transforms/CodeGenPrepare/NVPTX/bypass-slow-div.ll
Index: llvm/trunk/test/Transforms/CodeGenPrepare/NVPTX/bypass-slow-div.ll
===================================================================
--- llvm/trunk/test/Transforms/CodeGenPrepare/NVPTX/bypass-slow-div.ll
+++ llvm/trunk/test/Transforms/CodeGenPrepare/NVPTX/bypass-slow-div.ll
@@ -0,0 +1,29 @@
+; RUN: opt -S -codegenprepare < %s | FileCheck %s
+
+target datalayout = "e-i64:64-v16:16-v32:32-n16:32:64"
+target triple = "nvptx64-nvidia-cuda"
+
+; We only use the div instruction -- the rem should be DCE'ed.
+; CHECK-LABEL: @div_only
+define void @div_only(i64 %a, i64 %b, i64* %retptr) {
+ ; CHECK: udiv i32
+ ; CHECK-NOT: urem
+ ; CHECK: sdiv i64
+ ; CHECK-NOT: rem
+ %d = sdiv i64 %a, %b
+ store i64 %d, i64* %retptr
+ ret void
+}
+
+; We only use the rem instruction -- the div should be DCE'ed.
+; CHECK-LABEL: @rem_only
+define void @rem_only(i64 %a, i64 %b, i64* %retptr) {
+ ; CHECK-NOT: div
+ ; CHECK: urem i32
+ ; CHECK-NOT: div
+ ; CHECK: rem i64
+ ; CHECK-NOT: div
+ %d = srem i64 %a, %b
+ store i64 %d, i64* %retptr
+ ret void
+}
Index: llvm/trunk/lib/Transforms/Utils/BypassSlowDivision.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Utils/BypassSlowDivision.cpp
+++ llvm/trunk/lib/Transforms/Utils/BypassSlowDivision.cpp
@@ -20,6 +20,7 @@
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
+#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
@@ -246,5 +247,12 @@
MadeChange |= reuseOrInsertFastDiv(I, BT, UseDivOp, UseSignedOp, DivCache);
}
+ // Above we eagerly create divs and rems, as pairs, so that we can efficiently
+ // create divrem machine instructions. Now erase any unused divs / rems so we
+ // don't leave extra instructions sitting around.
+ for (auto &KV : DivCache)
+ for (Instruction *Phi : {KV.second.Quotient, KV.second.Remainder})
+ RecursivelyDeleteTriviallyDeadInstructions(Phi);
+
return MadeChange;
}
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