[PATCH] D56838: [CGP] Check for existing inttotpr before creating new one

[Roman Tereshin via Phabricator via llvm-commits]

rtereshin created this revision.
rtereshin added reviewers: qcolombet, marcello.maggioni.
Herald added subscribers: llvm-commits, javed.absar.

Make sure CodeGenPrepare doesn't emit multiple inttoptr instructions of
the same integer value while sinking address computations, but rather
CSEs them on the fly: excessive inttoptr's confuse SCEV into thinking
that related pointers have nothing to do with each other.

This problem blocks LoadStoreVectorizer from vectorizing some of the
loads / stores in a downstream target.


Repository:
  rL LLVM

https://reviews.llvm.org/D56838

Files:
  lib/CodeGen/CodeGenPrepare.cpp
  test/Transforms/CodeGenPrepare/X86/sink-addrmode-cse-inttoptrs.ll


Index: test/Transforms/CodeGenPrepare/X86/sink-addrmode-cse-inttoptrs.ll
===================================================================
--- /dev/null
+++ test/Transforms/CodeGenPrepare/X86/sink-addrmode-cse-inttoptrs.ll
@@ -0,0 +1,39 @@
+; RUN: opt -mtriple=x86_64-- -codegenprepare                        %s -S -o - | FileCheck %s --check-prefix=CGP
+; RUN: opt -mtriple=x86_64-- -codegenprepare -load-store-vectorizer %s -S -o - | FileCheck %s --check-prefix=LSV
+
+; Make sure CodeGenPrepare doesn't emit multiple inttoptr instructions
+; of the same integer value while sinking address computations, but
+; rather CSEs them on the fly: excessive inttoptr's confuse SCEV
+; into thinking that related pointers have nothing to do with each other.
+;
+; Triggering this problem involves having just right addressing modes,
+; and verifying that the motivating pass (LoadStoreVectorizer) is able
+; to benefit from it - just right LSV-policies. Hence the atypical combination
+; of the target and datalayout / address spaces in this test.
+
+target datalayout = "p1:32:32:32"
+
+define void @main(i32 %tmp, i32 %off) {
+; CGP:     = inttoptr
+; CGP-NOT: = inttoptr
+; LSV-NOT: = load float
+entry:
+  %tmp1 = inttoptr i32 %tmp to float addrspace(1)*
+  %arrayidx.i.7 = getelementptr inbounds float, float addrspace(1)* %tmp1, i32 %off
+  %add20.i.7 = add i32 %off, 1
+  %arrayidx22.i.7 = getelementptr inbounds float, float addrspace(1)* %tmp1, i32 %add20.i.7
+  br label %for.body
+
+for.body:
+  %tmp8 = phi float [ undef, %entry ], [ %tmp62, %for.body ]
+  %tmp28 = load float, float addrspace(1)* %arrayidx.i.7
+  %tmp29 = load float, float addrspace(1)* %arrayidx22.i.7
+  %arrayidx.i321.7 = getelementptr inbounds float, float addrspace(1)* %tmp1, i32 0
+  %tmp43 = load float, float addrspace(1)* %arrayidx.i321.7
+  %arrayidx22.i327.7 = getelementptr inbounds float, float addrspace(1)* %tmp1, i32 1
+  %tmp44 = load float, float addrspace(1)* %arrayidx22.i327.7
+  %tmp62 = tail call fast float @foo(float %tmp8, float %tmp44, float %tmp43, float %tmp29, float %tmp28)
+  br label %for.body
+}
+
+declare float @foo(float, float, float, float, float)
Index: lib/CodeGen/CodeGenPrepare.cpp
===================================================================
--- lib/CodeGen/CodeGenPrepare.cpp
+++ lib/CodeGen/CodeGenPrepare.cpp
@@ -4664,13 +4664,22 @@
     // will look through it and provide only the integer value. In that case,
     // use it here.
     if (!DL->isNonIntegralPointerType(Addr->getType())) {
+      const auto getResultPtr = [MemoryInst, Addr,
+                                 &Builder](Value *Reg) -> Value * {
+        for (User *U : Reg->users())
+          if (auto *I2P = dyn_cast<IntToPtrInst>(U))
+            if (I2P->getType() == Addr->getType() &&
+                I2P->getParent() == MemoryInst->getParent()) {
+              I2P->moveBefore(MemoryInst->getParent()->getFirstNonPHI());
+              return I2P;
+            }
+        return Builder.CreateIntToPtr(Reg, Addr->getType(), "sunkaddr");
+      };
       if (!ResultPtr && AddrMode.BaseReg) {
-        ResultPtr = Builder.CreateIntToPtr(AddrMode.BaseReg, Addr->getType(),
-                                           "sunkaddr");
+        ResultPtr = getResultPtr(AddrMode.BaseReg);
         AddrMode.BaseReg = nullptr;
       } else if (!ResultPtr && AddrMode.Scale == 1) {
-        ResultPtr = Builder.CreateIntToPtr(AddrMode.ScaledReg, Addr->getType(),
-                                           "sunkaddr");
+        ResultPtr = getResultPtr(AddrMode.ScaledReg);
         AddrMode.Scale = 0;
       }
     }


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