[llvm-commits] [llvm] r122043 - in /llvm/trunk: lib/MC/MCExpr.cpp test/MC/MachO/darwin-complex-difference.s
Daniel Dunbar
daniel at zuster.org
Thu Dec 16 21:50:34 PST 2010
Author: ddunbar
Date: Thu Dec 16 23:50:33 2010
New Revision: 122043
URL: http://llvm.org/viewvc/llvm-project?rev=122043&view=rev
Log:
MC/Expr: Implemnt more aggressive folding during symbol evaluation using
IsSymbolRefDifferenceFullyResolved(). For example, we will now fold away
something like:
--
_a:
...
L0:
...
L1:
...
.long (L1 - L0) / 2
--
Added:
llvm/trunk/test/MC/MachO/darwin-complex-difference.s
Modified:
llvm/trunk/lib/MC/MCExpr.cpp
Modified: llvm/trunk/lib/MC/MCExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCExpr.cpp?rev=122043&r1=122042&r2=122043&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCExpr.cpp (original)
+++ llvm/trunk/lib/MC/MCExpr.cpp Thu Dec 16 23:50:33 2010
@@ -271,6 +271,25 @@
return true;
}
+/// \brief Helper method for \see EvaluateSymbolAdd().
+static void AttemptToFoldSymbolOffsetDifference(const MCAsmLayout *Layout,
+ const MCSymbolRefExpr *&A,
+ const MCSymbolRefExpr *&B,
+ int64_t &Addend) {
+ const MCAssembler &Asm = Layout->getAssembler();
+
+ if (A && B &&
+ Asm.getWriter().IsSymbolRefDifferenceFullyResolved(Asm, A, B)) {
+ // Eagerly evaluate.
+ Addend += (Layout->getSymbolOffset(&Asm.getSymbolData(A->getSymbol())) -
+ Layout->getSymbolOffset(&Asm.getSymbolData(B->getSymbol())));
+
+ // Clear the symbol expr pointers to indicate we have folded these
+ // operands.
+ A = B = 0;
+ }
+}
+
/// \brief Evaluate the result of an add between (conceptually) two MCValues.
///
/// This routine conceptually attempts to construct an MCValue:
@@ -300,20 +319,37 @@
// Fold the result constant immediately.
int64_t Result_Cst = LHS_Cst + RHS_Cst;
+ // If we have a layout, we can fold resolved differences.
+ if (Layout) {
+ // First, fold out any differences which are fully resolved. By
+ // reassociating terms in
+ // Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
+ // we have the four possible differences:
+ // (LHS_A - LHS_B),
+ // (LHS_A - RHS_B),
+ // (RHS_A - LHS_B),
+ // (RHS_A - RHS_B).
+ // Since we are attempting to be as aggresive as possible about folding, we
+ // attempt to evaluate each possible alternative.
+ AttemptToFoldSymbolOffsetDifference(Layout, LHS_A, LHS_B, Result_Cst);
+ AttemptToFoldSymbolOffsetDifference(Layout, LHS_A, RHS_B, Result_Cst);
+ AttemptToFoldSymbolOffsetDifference(Layout, RHS_A, LHS_B, Result_Cst);
+ AttemptToFoldSymbolOffsetDifference(Layout, RHS_A, RHS_B, Result_Cst);
+ }
+
// We can't represent the addition or subtraction of two symbols.
if ((LHS_A && RHS_A) || (LHS_B && RHS_B))
return false;
+ // At this point, we have at most one additive symbol and one subtractive
+ // symbol -- find them.
const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A;
const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B;
- if (B) {
- // If we have a negated symbol, then we must have also have a non-negated
- // symbol in order to encode the expression. We can do this check later to
- // permit expressions which eventually fold to a representable form -- such
- // as (a + (0 - b)) -- if necessary.
- if (!A)
- return false;
- }
+
+ // If we have a negated symbol, then we must have also have a non-negated
+ // symbol in order to encode the expression.
+ if (B && !A)
+ return false;
// Absolutize symbol differences between defined symbols when we have a
// layout object and the target requests it.
Added: llvm/trunk/test/MC/MachO/darwin-complex-difference.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/MachO/darwin-complex-difference.s?rev=122043&view=auto
==============================================================================
--- llvm/trunk/test/MC/MachO/darwin-complex-difference.s (added)
+++ llvm/trunk/test/MC/MachO/darwin-complex-difference.s Thu Dec 16 23:50:33 2010
@@ -0,0 +1,129 @@
+// RUN: llvm-mc -triple x86_64-apple-darwin10 %s -filetype=obj -o %t.o
+// RUN: macho-dump --dump-section-data < %t.o > %t.dump
+// RUN: FileCheck < %t.dump %s
+
+_a:
+L0:
+ .long 1
+L1:
+ .long 2
+ .long _c - _d + 4
+ .long (_c - L0) - (_d - L1) // == (_c - _d) + (L1 - L0)
+ // == (_c - _d + 4)
+_c:
+ .long 0
+_d:
+ .long 0
+
+// CHECK: ('cputype', 16777223)
+// CHECK: ('cpusubtype', 3)
+// CHECK: ('filetype', 1)
+// CHECK: ('num_load_commands', 3)
+// CHECK: ('load_commands_size', 256)
+// CHECK: ('flag', 0)
+// CHECK: ('reserved', 0)
+// CHECK: ('load_commands', [
+// CHECK: # Load Command 0
+// CHECK: (('command', 25)
+// CHECK: ('size', 152)
+// CHECK: ('segment_name', '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
+// CHECK: ('vm_addr', 0)
+// CHECK: ('vm_size', 24)
+// CHECK: ('file_offset', 288)
+// CHECK: ('file_size', 24)
+// CHECK: ('maxprot', 7)
+// CHECK: ('initprot', 7)
+// CHECK: ('num_sections', 1)
+// CHECK: ('flags', 0)
+// CHECK: ('sections', [
+// CHECK: # Section 0
+// CHECK: (('section_name', '__text\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
+// CHECK: ('segment_name', '__TEXT\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
+// CHECK: ('address', 0)
+// CHECK: ('size', 24)
+// CHECK: ('offset', 288)
+// CHECK: ('alignment', 0)
+// CHECK: ('reloc_offset', 312)
+// CHECK: ('num_reloc', 4)
+// CHECK: ('flags', 0x80000000)
+// CHECK: ('reserved1', 0)
+// CHECK: ('reserved2', 0)
+// CHECK: ('reserved3', 0)
+// CHECK: ),
+// CHECK: ('_relocations', [
+// CHECK: # Relocation 0
+// CHECK: (('word-0', 0xc),
+// CHECK: ('word-1', 0x5c000002)),
+// CHECK: # Relocation 1
+// CHECK: (('word-0', 0xc),
+// CHECK: ('word-1', 0xc000001)),
+// CHECK: # Relocation 2
+// CHECK: (('word-0', 0x8),
+// CHECK: ('word-1', 0x5c000002)),
+// CHECK: # Relocation 3
+// CHECK: (('word-0', 0x8),
+// CHECK: ('word-1', 0xc000001)),
+// CHECK: ])
+// CHECK: ('_section_data', '01000000 02000000 04000000 04000000 00000000 00000000')
+// CHECK: ])
+// CHECK: ),
+// CHECK: # Load Command 1
+// CHECK: (('command', 2)
+// CHECK: ('size', 24)
+// CHECK: ('symoff', 344)
+// CHECK: ('nsyms', 3)
+// CHECK: ('stroff', 392)
+// CHECK: ('strsize', 12)
+// CHECK: ('_string_data', '\x00_a\x00_c\x00_d\x00\x00\x00')
+// CHECK: ('_symbols', [
+// CHECK: # Symbol 0
+// CHECK: (('n_strx', 1)
+// CHECK: ('n_type', 0xe)
+// CHECK: ('n_sect', 1)
+// CHECK: ('n_desc', 0)
+// CHECK: ('n_value', 0)
+// CHECK: ('_string', '_a')
+// CHECK: ),
+// CHECK: # Symbol 1
+// CHECK: (('n_strx', 4)
+// CHECK: ('n_type', 0xe)
+// CHECK: ('n_sect', 1)
+// CHECK: ('n_desc', 0)
+// CHECK: ('n_value', 16)
+// CHECK: ('_string', '_c')
+// CHECK: ),
+// CHECK: # Symbol 2
+// CHECK: (('n_strx', 7)
+// CHECK: ('n_type', 0xe)
+// CHECK: ('n_sect', 1)
+// CHECK: ('n_desc', 0)
+// CHECK: ('n_value', 20)
+// CHECK: ('_string', '_d')
+// CHECK: ),
+// CHECK: ])
+// CHECK: ),
+// CHECK: # Load Command 2
+// CHECK: (('command', 11)
+// CHECK: ('size', 80)
+// CHECK: ('ilocalsym', 0)
+// CHECK: ('nlocalsym', 3)
+// CHECK: ('iextdefsym', 3)
+// CHECK: ('nextdefsym', 0)
+// CHECK: ('iundefsym', 3)
+// CHECK: ('nundefsym', 0)
+// CHECK: ('tocoff', 0)
+// CHECK: ('ntoc', 0)
+// CHECK: ('modtaboff', 0)
+// CHECK: ('nmodtab', 0)
+// CHECK: ('extrefsymoff', 0)
+// CHECK: ('nextrefsyms', 0)
+// CHECK: ('indirectsymoff', 0)
+// CHECK: ('nindirectsyms', 0)
+// CHECK: ('extreloff', 0)
+// CHECK: ('nextrel', 0)
+// CHECK: ('locreloff', 0)
+// CHECK: ('nlocrel', 0)
+// CHECK: ('_indirect_symbols', [
+// CHECK: ])
+// CHECK: ),
+// CHECK: ])
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