ScopInfo: Never add read accesses for synthesizable values

Before adding a MK_Value READ MemoryAccess, check whether the read is
necessary or synthesizable. Synthesizable values are later generated by
the SCEVExpander and therefore do not need to be transferred
explicitly. This can happen because the check for synthesizability has
presumbly been forgotten in the case where a phi's incoming value has
been defined in a different statement.

Differential Revision: http://reviews.llvm.org/D15687

llvm-svn: 258998

polly/lib/Analysis/ScopInfo.cpp

@@ -3962,6 +3962,13 @@ void ScopInfo::ensureValueWrite(Instruction *Value) {
                   ArrayRef<const SCEV *>(), ScopArrayInfo::MK_Value);
 }
 void ScopInfo::ensureValueRead(Value *Value, BasicBlock *UserBB) {
+
+  // If the instruction can be synthesized and the user is in the region we do
+  // not need to add a value dependences.
+  Region &ScopRegion = scop->getRegion();
+  if (canSynthesize(Value, LI, SE, &ScopRegion))
+    return;
+
   ScopStmt *UserStmt = scop->getStmtForBasicBlock(UserBB);
 
   // We do not model uses outside the scop.

polly/test/Isl/CodeGen/phi-defined-before-scop.ll

@@ -4,8 +4,7 @@
 ; CHECK-NEXT: %tmp7.ph.merge = phi %struct.wibble* [ %tmp7.ph.final_reload, %polly.exiting ], [ %tmp7.ph, %bb6.region_exiting ]
 
 ; CHECK-LABEL: polly.stmt.bb3:
-; CHECK-NEXT: %tmp2.s2a.reload = load %struct.wibble*, %struct.wibble** %tmp2.s2a
+; CHECK-NEXT: store %struct.wibble* %tmp2, %struct.wibble** %tmp7.s2a
-; CHECK-NEXT: store %struct.wibble* %tmp2.s2a.reload, %struct.wibble** %tmp7.s2a
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 

polly/test/Isl/CodeGen/synthesizable_phi_write_after_loop.ll

@@ -8,17 +8,11 @@
 ;         In this case the Loop passed to the expander must NOT be the loop
 ; - Overwriting the same alloca in each iteration s.t. the last value will
 ;         retain in %i.inc.s2a
-; The latter is currently generated by Polly and tested here.
+; The first is currently generated by Polly and tested here.
 
 ; CHECK:      polly.stmt.next:
-; CHECK-NEXT:   %i.inc.s2a.reload = load i32, i32* %i.inc.s2a
+; CHECK-NEXT:   store i32 2, i32* %phi.phiops
-; CHECK-NEXT:   store i32 %i.inc.s2a.reload, i32* %phi.phiops
 ; CHECK-NEXT:   br label %polly.stmt.join
-;
-; CHECK:      polly.stmt.loop:
-; CHECK:        %0 = trunc i64 %polly.indvar to i32
-; CHECK:        %1 = add i32 %0, 1
-; CHECK:        store i32 %1, i32* %i.inc.s2a
 
 define i32 @func() {
 entry:

polly/test/Isl/CodeGen/uninitialized_scalar_memory.ll

@@ -5,7 +5,6 @@
 ;
 ; CHECK:      polly.start:
 ; CHECK-NEXT:   store float %ebig.0, float* %ebig.0.s2a
-; CHECK-NEXT:   store i32 %iebig.0, i32* %iebig.0.s2a
 ; CHECK-NEXT:   br label %polly.stmt.if.end.entry
 ;
 ;    int g(void);

polly/test/ScopInfo/NonAffine/non_affine_loop_used_later.ll

@@ -25,7 +25,6 @@
 ; CHECK-NEXT:     i32 MemRef_j_0__phi; // Element size 4
 ; CHECK-NEXT:     i32 MemRef_j_0; // Element size 4
 ; CHECK-NEXT:     i32 MemRef_A[*]; // Element size 4
-; CHECK-NEXT:     i32 MemRef_smax; // Element size 4
 ; CHECK-NEXT:     i32 MemRef_j_2__phi; // Element size 4
 ; CHECK-NEXT:     i32 MemRef_j_2; // Element size 4
 ; CHECK-NEXT: }
@@ -33,7 +32,6 @@
 ; CHECK-NEXT:     i32 MemRef_j_0__phi; // Element size 4
 ; CHECK-NEXT:     i32 MemRef_j_0; // Element size 4
 ; CHECK-NEXT:     i32 MemRef_A[*]; // Element size 4
-; CHECK-NEXT:     i32 MemRef_smax; // Element size 4
 ; CHECK-NEXT:     i32 MemRef_j_2__phi; // Element size 4
 ; CHECK-NEXT:     i32 MemRef_j_2; // Element size 4
 ; CHECK-NEXT: }
@@ -60,8 +58,6 @@
 ; CHECK-NEXT:             [N] -> { Stmt_bb4__TO__bb18[i0] -> MemRef_A[i0] };
 ; CHECK-NEXT:         MayWriteAccess :=    [Reduction Type: NONE] [Scalar: 0]
 ; CHECK-NEXT:             [N] -> { Stmt_bb4__TO__bb18[i0] -> MemRef_A[i0] };
-; CHECK-NEXT:         ReadAccess :=    [Reduction Type: NONE] [Scalar: 1]
-; CHECK-NEXT:             [N] -> { Stmt_bb4__TO__bb18[i0] -> MemRef_smax[] };
 ; CHECK-NEXT:         MustWriteAccess :=    [Reduction Type: NONE] [Scalar: 1]
 ; CHECK-NEXT:             [N] -> { Stmt_bb4__TO__bb18[i0] -> MemRef_j_2__phi[] };
 ; CHECK-NEXT:         ReadAccess :=    [Reduction Type: NONE] [Scalar: 1]

polly/test/ScopInfo/non_affine_region_1.ll

@@ -41,8 +41,6 @@
 ; CHECK-NEXT:             [b] -> { Stmt_bb8[0] : b = 0 };
 ; CHECK-NEXT:         Schedule :=
 ; CHECK-NEXT:             [b] -> { Stmt_bb8[i0] -> [0, 0] };
-; CHECK-NEXT:         ReadAccess :=    [Reduction Type: NONE] [Scalar: 1]
-; CHECK-NEXT:             [b] -> { Stmt_bb8[i0] -> MemRef_b[] };
 ; CHECK-NEXT:         MustWriteAccess :=    [Reduction Type: NONE] [Scalar: 1]
 ; CHECK-NEXT:             [b] -> { Stmt_bb8[i0] -> MemRef_x_1__phi[] };
 ; CHECK-NEXT:     Stmt_bb10__TO__bb18

polly/test/ScopInfo/non_affine_region_3.ll

@@ -31,8 +31,6 @@
 ; CHECK-NEXT:              { Stmt_bb3__TO__bb18[i0] -> MemRef_A[i0] };
 ; CHECK-NEXT:          MustWriteAccess :=    [Reduction Type: NONE] [Scalar: 1]
 ; CHECK-NEXT:              { Stmt_bb3__TO__bb18[i0] -> MemRef_x_2__phi[] };
-; CHECK-NEXT:          ReadAccess :=    [Reduction Type: NONE] [Scalar: 1]
-; CHECK-NEXT:              { Stmt_bb3__TO__bb18[i0] -> MemRef_b[] };
 ; CHECK-NEXT:      Stmt_bb18
 ; CHECK-NEXT:          Domain :=
 ; CHECK-NEXT:              { Stmt_bb18[i0] : 0 <= i0 <= 1023 };

polly/test/ScopInfo/pointer-used-as-base-pointer-and-scalar-read.ll

@@ -6,16 +6,12 @@
 
 ; CHECK:      Arrays {
 ; CHECK-NEXT:     float MemRef_A[*]; // Element size 4
-; CHECK-NEXT:     float* MemRef_A; // Element size 8
 ; CHECK-NEXT:     float* MemRef_x__phi; // Element size 8
-; CHECK-NEXT:     float* MemRef_B; // Element size 8
 ; CHECK-NEXT:     float* MemRef_C[*]; // Element size 8
 ; CHECK-NEXT: }
 ; CHECK:      Arrays (Bounds as pw_affs) {
 ; CHECK-NEXT:     float MemRef_A[*]; // Element size 4
-; CHECK-NEXT:     float* MemRef_A; // Element size 8
 ; CHECK-NEXT:     float* MemRef_x__phi; // Element size 8
-; CHECK-NEXT:     float* MemRef_B; // Element size 8
 ; CHECK-NEXT:     float* MemRef_C[*]; // Element size 8
 ; CHECK-NEXT: }
 ; CHECK:      Alias Groups (0):
@@ -28,8 +24,6 @@
 ; CHECK-NEXT:             [p] -> { Stmt_then[i0] -> [i0, 1] };
 ; CHECK-NEXT:         MustWriteAccess :=    [Reduction Type: NONE] [Scalar: 0]
 ; CHECK-NEXT:             [p] -> { Stmt_then[i0] -> MemRef_A[0] };
-; CHECK-NEXT:         ReadAccess :=    [Reduction Type: NONE] [Scalar: 1]
-; CHECK-NEXT:             [p] -> { Stmt_then[i0] -> MemRef_A[] };
 ; CHECK-NEXT:         MustWriteAccess :=    [Reduction Type: NONE] [Scalar: 1]
 ; CHECK-NEXT:             [p] -> { Stmt_then[i0] -> MemRef_x__phi[] };
 ; CHECK-NEXT:     Stmt_else
@@ -39,8 +33,6 @@
 ; CHECK-NEXT:             [p] -> { Stmt_else[i0] -> [i0, 0] : p >= 33 or p <= 31 };
 ; CHECK-NEXT:         MustWriteAccess :=    [Reduction Type: NONE] [Scalar: 0]
 ; CHECK-NEXT:             [p] -> { Stmt_else[i0] -> MemRef_A[0] };
-; CHECK-NEXT:         ReadAccess :=    [Reduction Type: NONE] [Scalar: 1]
-; CHECK-NEXT:             [p] -> { Stmt_else[i0] -> MemRef_B[] };
 ; CHECK-NEXT:         MustWriteAccess :=    [Reduction Type: NONE] [Scalar: 1]
 ; CHECK-NEXT:             [p] -> { Stmt_else[i0] -> MemRef_x__phi[] };
 ; CHECK-NEXT:     Stmt_bb8

polly/test/ScopInfo/same-base-address-scalar-and-array.ll

@@ -4,7 +4,6 @@
 ; as it is used as a memory base pointer (%0) but also as a scalar (%out.addr.0.lcssa).
 ;
 ; CHECK:         Arrays {
-; CHECK-NEXT:        float* MemRef_out; // Element size 8
 ; CHECK-NEXT:        float* MemRef_out_addr_0_lcssa; // Element size 8
 ; CHECK-NEXT:        float MemRef_out[*]; // Element size 4
 ; CHECK-NEXT:    }