Changeset 938885d3

Timestamp:

May 6, 2021, 11:11:09 AM (4 years ago)

Author:

Michael Brooks <mlbrooks@…>

Branches:

ADT, arm-eh, ast-experimental, enum, forall-pointer-decay, jacob/cs343-translation, master, new-ast-unique-expr, pthread-emulation, qualifiedEnum

Children:

3e1a705, b721578

Parents:

8464edf

Message:

Fixing a false failure of the new array test on x86-32 -O3.

File:

• tests/array-container/array-md-sbscr-cases.cfa (modified) (5 diffs)

tests/array-container/array-md-sbscr-cases.cfa

@@ -27 +27 @@
 }
 
+// Work around a compiler optimization that can lead to false failures.
+// Think of `valExpected` as a constant local to each test function.
+// When implemented that way, an optimization, run on some hardware, makes
+// its value be off-by-a-little, compared with the values that have been
+// stored-loaded (in the array under test).  This effect has been observed
+// on x86-32 with -O3.  Declaring it as below forces the expected value 
+// to be stored-loaded too, which keeps the (admittedly lazily done)
+// `assert(f1 == f2)` checks passing, when the intended <w,x,y,z> location
+// is recovered, which is the point of all these tests.
+volatile float valExpected = 0.0;
+
 // Tests all the ways to split dimensions into CFA-supported chunks, by the only order that C supports: coarsest to finest stride.
 forall( [Nw], [Nx], [Ny], [Nz] )
@@ -36 +47 @@
     ptrdiff_t iw = 2, ix = 3, iy=4, iz=5;
 
-    const float valExpected = getMagicNumber(iw, ix, iy, iz);
-    assert( wxyz[iw][ix][iy][iz] == valExpected );
+    valExpected = getMagicNumber(iw, ix, iy, iz);
+    float valGot = wxyz[iw][ix][iy][iz];
+    assert( valGot == valExpected );
 
     // order wxyz, natural split (4-0 or 0-4, no intermediate to declare)
@@ -86 +98 @@
     ptrdiff_t iw = 2, ix = 3, iy=4, iz=5;
 
-    const float valExpected = getMagicNumber(iw, ix, iy, iz);
+    valExpected = getMagicNumber(iw, ix, iy, iz);
     assert( wxyz[iw][ix][iy][iz] == valExpected );
 
@@ -129 +141 @@
     ptrdiff_t iw = 2, ix = 3, iy=4, iz=5;
 
-    const float valExpected = getMagicNumber(iw, ix, iy, iz);
+    valExpected = getMagicNumber(iw, ix, iy, iz);
     assert( wxyz[iw][ix][iy][iz] == valExpected );
 
@@ -225 +237 @@
     fillHelloData(wxyz);
 
-    const float valExpected = getMagicNumber(2, 3, 4, 5);
+    valExpected = getMagicNumber(2, 3, 4, 5);
     assert(( wxyz [2] [3] [4] [5]  == valExpected ));
     assert(( wxyz[[2,  3]][4] [5]  == valExpected ));