[PATCH] [GVN] Use a simpler form of IRBuilder constructor.

[Alexey Samsonov]

Hi echristo, dberlin, dblaikie,

A side effect of this change is that it IRBuilder now automatically
created debug info locations for new instructions, which is the
same as debug location of insertion point. This is fine for the
functions in questions (GetStoreValueForLoad and
GetMemInstValueForLoad), as they are used in two situations:
  * GVN::processLoad, which tries to eliminate a load. In this case
    new instructions would have the same debug location as the load they
    eventually replace;
  * MaterializeAdjustedValue, which adds new instructions to the end
    of the basic blocks, which could later be used to replace the load
    definition. In this case we don't yet know the way the load would
    be eventually replaced (either by assembling the precomputed values
    via PHI, or by using them directly), so just using the basic block
    strategy seems to be reasonable. There is also a special case
    in the code that *would* adjust the location of the last
    instruction replacing the load definition to the location of the
    load.

http://reviews.llvm.org/D10405

Files:
  lib/Transforms/Scalar/GVN.cpp
  test/Transforms/GVN/load-pre-nonlocal.ll

Index: lib/Transforms/Scalar/GVN.cpp
===================================================================
--- lib/Transforms/Scalar/GVN.cpp
+++ lib/Transforms/Scalar/GVN.cpp
@@ -1120,7 +1120,7 @@
   uint64_t StoreSize = (DL.getTypeSizeInBits(SrcVal->getType()) + 7) / 8;
   uint64_t LoadSize = (DL.getTypeSizeInBits(LoadTy) + 7) / 8;
 
-  IRBuilder<> Builder(InsertPt->getParent(), InsertPt);
+  IRBuilder<> Builder(InsertPt);
 
   // Compute which bits of the stored value are being used by the load.  Convert
   // to an integer type to start with.
@@ -1217,7 +1217,7 @@
   LLVMContext &Ctx = LoadTy->getContext();
   uint64_t LoadSize = DL.getTypeSizeInBits(LoadTy)/8;
 
-  IRBuilder<> Builder(InsertPt->getParent(), InsertPt);
+  IRBuilder<> Builder(InsertPt);
 
   // We know that this method is only called when the mem transfer fully
   // provides the bits for the load.
Index: test/Transforms/GVN/load-pre-nonlocal.ll
===================================================================
--- test/Transforms/GVN/load-pre-nonlocal.ll
+++ test/Transforms/GVN/load-pre-nonlocal.ll
@@ -53,35 +53,55 @@
 ; %1 is partially redundant if %0 can be widened to a 64-bit load.
 
 ; CHECK-LABEL: define i32 @overaligned_load
+; CHECK: if.then:
+; CHECK:   %0 = load i64
+; CHECK:   [[LSHR:%[0-9]+]] = lshr i64 %0, 32, !dbg [[LSHR_LOC:![0-9]+]]
+; CHECK:   trunc i64 [[LSHR]] to i32
 ; CHECK: if.end:
 ; CHECK-NOT: %1 = load i32, i32*
+; CHECK: [[LSHR_LOC]] = !DILocation(line: 101, column: 1, scope: !{{.*}})
 
 define i32 @overaligned_load(i32 %a, i32* nocapture %b) {
 entry:
-  %cmp = icmp sgt i32 %a, 0
-  br i1 %cmp, label %if.then, label %if.else
+  %cmp = icmp sgt i32 %a, 0, !dbg !14
+  br i1 %cmp, label %if.then, label %if.else, !dbg !14
 
 if.then:
-  %0 = load i32, i32* getelementptr inbounds (%struct.S1, %struct.S1* @s1, i64 0, i32 0), align 8, !tbaa !5
-  br label %if.end
+  %0 = load i32, i32* getelementptr inbounds (%struct.S1, %struct.S1* @s1, i64 0, i32 0), align 8, !tbaa !5, !dbg !15
+  br label %if.end, !dbg !15
 
 if.else:
-  %arrayidx = getelementptr inbounds i32, i32* %b, i64 2
-  store i32 10, i32* %arrayidx, align 4, !tbaa !5
-  br label %if.end
+  %arrayidx = getelementptr inbounds i32, i32* %b, i64 2, !dbg !16
+  store i32 10, i32* %arrayidx, align 4, !tbaa !5, !dbg !16
+  br label %if.end, !dbg !16
 
 if.end:
   %i.0 = phi i32 [ %0, %if.then ], [ 0, %if.else ]
   %p.0 = phi i32* [ getelementptr inbounds (%struct.S1, %struct.S1* @s1, i64 0, i32 0), %if.then ], [ %b, %if.else ]
-  %add.ptr = getelementptr inbounds i32, i32* %p.0, i64 1
-  %1 = load i32, i32* %add.ptr, align 4, !tbaa !5
-  %add1 = add nsw i32 %1, %i.0
-  ret i32 %add1
+  %add.ptr = getelementptr inbounds i32, i32* %p.0, i64 1, !dbg !17
+  %1 = load i32, i32* %add.ptr, align 4, !tbaa !5, !dbg !17
+  %add1 = add nsw i32 %1, %i.0, !dbg !17
+  ret i32 %add1, !dbg !17
 }
 
 !1 = !{!2, !2, i64 0}
 !2 = !{!"any pointer", !3, i64 0}
 !3 = !{!"omnipotent char", !4, i64 0}
 !4 = !{!"Simple C/C++ TBAA"}
 !5 = !{!6, !6, i64 0}
 !6 = !{!"int", !3, i64 0}
+
+!llvm.module.flags = !{!7, !8, !9}
+!7 = !{i32 2, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 1, !"PIC Level", i32 2}
+
+!10 = !{}
+!11 = !DISubroutineType(types: !10)
+!12 = !DIFile(filename: "test.cpp", directory: "/tmp")
+!13 = !DISubprogram(name: "test", scope: !12, file: !12, line: 99, type: !11, isLocal: false, isDefinition: true, scopeLine: 100, flags: DIFlagPrototyped, isOptimized: false, function: i32 (i32, i32*)* @overaligned_load, variables: !10)
+!14 = !DILocation(line: 100, column: 1, scope: !13)
+!15 = !DILocation(line: 101, column: 1, scope: !13)
+!16 = !DILocation(line: 102, column: 1, scope: !13)
+!17 = !DILocation(line: 103, column: 1, scope: !13)
+

EMAIL PREFERENCES
  http://reviews.llvm.org/settings/panel/emailpreferences/
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